sql script: Graphs, Trees, Hierarchies and Recursive Queries

---------------------------------------------------------------------
-- Inside Microsoft SQL Server 2008: T-SQL Querying (MSPress, 2009)
-- Chapter 12 - Graphs, Trees, Hierarchies and Recursive Queries
-- Copyright Itzik Ben-Gan, 2009
-- All Rights Reserved
---------------------------------------------------------------------

---------------------------------------------------------------------
-- Scenarios
---------------------------------------------------------------------

---------------------------------------------------------------------
-- Employees Organizational Chart
---------------------------------------------------------------------

-- Listing 12-1: DDL & Sample Data for Employees
SET NOCOUNT ON;
USE tempdb;
GO
IF OBJECT_ID('dbo.Employees') IS NOT NULL
  DROP TABLE dbo.Employees;
GO
CREATE TABLE dbo.Employees
(
  empid   INT         NOT NULL PRIMARY KEY,
  mgrid   INT         NULL     REFERENCES dbo.Employees,
  empname VARCHAR(25) NOT NULL,
  salary  MONEY       NOT NULL,
  CHECK (empid <> mgrid)
);

INSERT INTO dbo.Employees(empid, mgrid, empname, salary) VALUES
  (1,  NULL, 'David'  , $10000.00),
  (2,  1,    'Eitan'  ,  $7000.00),
  (3,  1,    'Ina'    ,  $7500.00),
  (4,  2,    'Seraph' ,  $5000.00),
  (5,  2,    'Jiru'   ,  $5500.00),
  (6,  2,    'Steve'  ,  $4500.00),
  (7,  3,    'Aaron'  ,  $5000.00),
  (8,  5,    'Lilach' ,  $3500.00),
  (9,  7,    'Rita'   ,  $3000.00),
  (10, 5,    'Sean'   ,  $3000.00),
  (11, 7,    'Gabriel',  $3000.00),
  (12, 9,    'Emilia' ,  $2000.00),
  (13, 9,    'Michael',  $2000.00),
  (14, 9,    'Didi'   ,  $1500.00);

CREATE UNIQUE INDEX idx_unc_mgrid_empid ON dbo.Employees(mgrid, empid);
GO

---------------------------------------------------------------------
-- Bill Of Materials (BOM)
---------------------------------------------------------------------

-- Listing 12-2: DDL & Sample Data for Parts, BOM
SET NOCOUNT ON;
USE tempdb;
GO
IF OBJECT_ID('dbo.BOM') IS NOT NULL
  DROP TABLE dbo.BOM;
GO
IF OBJECT_ID('dbo.Parts') IS NOT NULL
  DROP TABLE dbo.Parts;
GO
CREATE TABLE dbo.Parts
(
  partid   INT         NOT NULL PRIMARY KEY,
  partname VARCHAR(25) NOT NULL
);

INSERT INTO dbo.Parts(partid, partname) VALUES
  ( 1, 'Black Tea'      ),
  ( 2, 'White Tea'      ),
  ( 3, 'Latte'          ),
  ( 4, 'Espresso'       ),
  ( 5, 'Double Espresso'),
  ( 6, 'Cup Cover'      ),
  ( 7, 'Regular Cup'    ),
  ( 8, 'Stirrer'        ),
  ( 9, 'Espresso Cup'   ),
  (10, 'Tea Shot'       ),
  (11, 'Milk'           ),
  (12, 'Coffee Shot'    ),
  (13, 'Tea Leaves'     ),
  (14, 'Water'          ),
  (15, 'Sugar Bag'      ),
  (16, 'Ground Coffee'  ),
  (17, 'Coffee Beans'   );

CREATE TABLE dbo.BOM
(
  partid     INT           NOT NULL REFERENCES dbo.Parts,
  assemblyid INT           NULL     REFERENCES dbo.Parts,
  unit       VARCHAR(3)    NOT NULL,
  qty        DECIMAL(8, 2) NOT NULL,
  UNIQUE(partid, assemblyid),
  CHECK (partid <> assemblyid)
);

INSERT INTO dbo.BOM(partid, assemblyid, unit, qty) VALUES
  ( 1, NULL, 'EA',   1.00),
  ( 2, NULL, 'EA',   1.00),
  ( 3, NULL, 'EA',   1.00),
  ( 4, NULL, 'EA',   1.00),
  ( 5, NULL, 'EA',   1.00),
  ( 6,    1, 'EA',   1.00),
  ( 7,    1, 'EA',   1.00),
  (10,    1, 'EA',   1.00),
  (14,    1, 'mL', 230.00),
  ( 6,    2, 'EA',   1.00),
  ( 7,    2, 'EA',   1.00),
  (10,    2, 'EA',   1.00),
  (14,    2, 'mL', 205.00),
  (11,    2, 'mL',  25.00),
  ( 6,    3, 'EA',   1.00),
  ( 7,    3, 'EA',   1.00),
  (11,    3, 'mL', 225.00),
  (12,    3, 'EA',   1.00),
  ( 9,    4, 'EA',   1.00),
  (12,    4, 'EA',   1.00),
  ( 9,    5, 'EA',   1.00),
  (12,    5, 'EA',   2.00),
  (13,   10, 'g' ,   5.00),
  (14,   10, 'mL',  20.00),
  (14,   12, 'mL',  20.00),
  (16,   12, 'g' ,  15.00),
  (17,   16, 'g' ,  15.00);
GO

---------------------------------------------------------------------
-- Road System
---------------------------------------------------------------------

-- Listing 12-3: DDL & Sample Data for Cities, Roads
SET NOCOUNT ON;
USE tempdb;
GO
IF OBJECT_ID('dbo.Roads') IS NOT NULL
  DROP TABLE dbo.Roads;
GO
IF OBJECT_ID('dbo.Cities') IS NOT NULL
  DROP TABLE dbo.Cities;
GO

CREATE TABLE dbo.Cities
(
  cityid  CHAR(3)     NOT NULL PRIMARY KEY,
  city    VARCHAR(30) NOT NULL,
  region  VARCHAR(30) NULL,
  country VARCHAR(30) NOT NULL
);

INSERT INTO dbo.Cities(cityid, city, region, country) VALUES
  ('ATL', 'Atlanta', 'GA', 'USA'),
  ('ORD', 'Chicago', 'IL', 'USA'),
  ('DEN', 'Denver', 'CO', 'USA'),
  ('IAH', 'Houston', 'TX', 'USA'),
  ('MCI', 'Kansas City', 'KS', 'USA'),
  ('LAX', 'Los Angeles', 'CA', 'USA'),
  ('MIA', 'Miami', 'FL', 'USA'),
  ('MSP', 'Minneapolis', 'MN', 'USA'),
  ('JFK', 'New York', 'NY', 'USA'),
  ('SEA', 'Seattle', 'WA', 'USA'),
  ('SFO', 'San Francisco', 'CA', 'USA'),
  ('ANC', 'Anchorage', 'AK', 'USA'),
  ('FAI', 'Fairbanks', 'AK', 'USA');

CREATE TABLE dbo.Roads
(
  city1       CHAR(3) NOT NULL REFERENCES dbo.Cities,
  city2       CHAR(3) NOT NULL REFERENCES dbo.Cities,
  distance INT     NOT NULL,
  PRIMARY KEY(city1, city2),
  CHECK(city1 < city2),
  CHECK(distance > 0)
);

INSERT INTO dbo.Roads(city1, city2, distance) VALUES
  ('ANC', 'FAI',  359),
  ('ATL', 'ORD',  715),
  ('ATL', 'IAH',  800),
  ('ATL', 'MCI',  805),
  ('ATL', 'MIA',  665),
  ('ATL', 'JFK',  865),
  ('DEN', 'IAH', 1120),
  ('DEN', 'MCI',  600),
  ('DEN', 'LAX', 1025),
  ('DEN', 'MSP',  915),
  ('DEN', 'SEA', 1335),
  ('DEN', 'SFO', 1270),
  ('IAH', 'MCI',  795),
  ('IAH', 'LAX', 1550),
  ('IAH', 'MIA', 1190),
  ('JFK', 'ORD',  795),
  ('LAX', 'SFO',  385),
  ('MCI', 'ORD',  525),
  ('MCI', 'MSP',  440),
  ('MSP', 'ORD',  410),
  ('MSP', 'SEA', 2015),
  ('SEA', 'SFO',  815);
GO

---------------------------------------------------------------------
-- Iterations/Recursion
---------------------------------------------------------------------

---------------------------------------------------------------------
-- Subordinates
---------------------------------------------------------------------

-- Creation Script for Function Subordinates1

---------------------------------------------------------------------
-- Function: Subordinates1, Descendants
--
-- Input   : @root INT: Manager id
--
-- Output  : @Subs Table: id and level of subordinates of
--                        input manager (empid = @root) in all levels
--
-- Process : * Insert into @Subs row of input manager
--           * In a loop, while previous insert loaded more than 0 rows
--             insert into @Subs next level of subordinates
---------------------------------------------------------------------
USE tempdb;
GO
IF OBJECT_ID('dbo.Subordinates1') IS NOT NULL
  DROP FUNCTION dbo.Subordinates1;
GO
CREATE FUNCTION dbo.Subordinates1(@root AS INT) RETURNS @Subs Table
(
  empid INT NOT NULL PRIMARY KEY NONCLUSTERED,
  lvl   INT NOT NULL,
  UNIQUE CLUSTERED(lvl, empid)  -- Index will be used to filter level 按级数筛选时用的索引
)
AS
BEGIN
  DECLARE @lvl AS INT = 0;      -- Initialize level counter with 0 初始化计数器为0

  -- Insert root node to @Subs
  INSERT INTO @Subs(empid, lvl)
    SELECT empid, @lvl FROM dbo.Employees WHERE empid = @root;

  WHILE @@rowcount > 0          -- while previous level had rows 当上一级存在行
  BEGIN
    SET @lvl = @lvl + 1;        -- Increment level counter 递增级数计数器

    -- Insert next level of subordinates to @Subs
    INSERT INTO @Subs(empid, lvl)
      SELECT C.empid, @lvl
      FROM @Subs AS P           -- P = Parent
        JOIN dbo.Employees AS C -- C = Child
          ON P.lvl = @lvl - 1   -- Filter parents from previous level 筛选上一级的父节点
          AND C.mgrid = P.empid;
  END

  RETURN;
END
GO

-- Node ids of descendants of a given node返回员工ID3的下属
SELECT empid, lvl FROM dbo.Subordinates1(3) AS S;

-- Descendants of a given node
SELECT E.empid, E.empname, S.lvl
FROM dbo.Subordinates1(3) AS S
  JOIN dbo.Employees AS E
    ON E.empid = S.empid;

-- Leaf nodes underneath a given node
SELECT empid
FROM dbo.Subordinates1(3) AS P
WHERE NOT EXISTS
  (SELECT * FROM dbo.Employees AS C
   WHERE C.mgrid = P.empid);

-- Subtree of a Given Root, CTE Solution 锚点成员，返回
DECLARE @root AS INT = 3;
WITH Subs
AS
(
  -- Anchor member returns root node
  SELECT empid, empname, 0 AS lvl
  FROM dbo.Employees
  WHERE empid = @root
  UNION ALL
  -- Recursive member returns next level of children
  SELECT C.empid, C.empname, P.lvl + 1
  FROM Subs AS P
    JOIN dbo.Employees AS C
      ON C.mgrid = P.empid
)
SELECT * FROM Subs;

-- Creation Script for Function PartsExplosion

---------------------------------------------------------------------
-- Function: PartsExplosion, Parts Explosion 零件分解 另：产品零件组合
--
-- Input   : @root INT: Root part id
--
-- Output  : @PartsExplosion Table:
--              id and level of contained parts of input part
--              in all levels
--
-- Process : * Insert into @PartsExplosion row of input root part
--           * In a loop, while previous insert loaded more than 0 rows
--             insert into @PartsExplosion next level of parts
---------------------------------------------------------------------
USE tempdb;
GO
IF OBJECT_ID('dbo.PartsExplosion') IS NOT NULL
  DROP FUNCTION dbo.PartsExplosion;
GO
CREATE FUNCTION dbo.PartsExplosion(@root AS INT)
  RETURNS @PartsExplosion Table
(
  partid INT           NOT NULL,
  qty    DECIMAL(8, 2) NOT NULL,
  unit   VARCHAR(3)    NOT NULL,
  lvl    INT           NOT NULL,
  n      INT           NOT NULL IDENTITY, -- surrogate key 代理键
  UNIQUE CLUSTERED(lvl, n)  -- Index will be used to filter lvl 用索引号LVL进行筛选
)
AS
BEGIN
  DECLARE @lvl AS INT = 0;                -- Initialize level counter with 0

  -- Insert root node to @PartsExplosion
  INSERT INTO @PartsExplosion(partid, qty, unit, lvl)
    SELECT partid, qty, unit, @lvl
    FROM dbo.BOM
    WHERE partid = @root;

  WHILE @@rowcount > 0           -- while previous level had rows
  BEGIN
    SET @lvl = @lvl + 1;         -- Increment level counter

    -- Insert next level of subordinates to @PartsExplosion
    INSERT INTO @PartsExplosion(partid, qty, unit, lvl)
      SELECT C.partid, P.qty * C.qty, C.unit, @lvl
      FROM @PartsExplosion AS P  -- P = Parent
        JOIN dbo.BOM AS C        -- C = Child
          ON P.lvl = @lvl - 1    -- Filter parents from previous level
          AND C.assemblyid = P.partid;
  END

  RETURN;
END
GO

-- Parts Explosion   UDF CTE	返回White Tea 的零部件
SELECT P.partid, P.partname, PE.qty, PE.unit, PE.lvl
FROM dbo.PartsExplosion(2) AS PE
  JOIN dbo.Parts AS P
    ON P.partid = PE.partid;

-- CTE Solution for Parts Explosion
DECLARE @root AS INT = 2;

WITH PartsExplosion
AS
(
  -- Anchor member returns root part
  SELECT partid, qty, unit, 0 AS lvl
  FROM dbo.BOM
  WHERE partid = @root

  UNION ALL

  -- Recursive member returns next level of parts
  SELECT C.partid, CAST(P.qty * C.qty AS DECIMAL(8, 2)),
    C.unit, P.lvl + 1
  FROM PartsExplosion AS P
    JOIN dbo.BOM AS C
      ON C.assemblyid = P.partid
)
SELECT P.partid, P.partname, PE.qty, PE.unit, PE.lvl
FROM PartsExplosion AS PE
  JOIN dbo.Parts AS P
    ON P.partid = PE.partid;
GO

-- Parts Explosion, Aggregating Parts
SELECT P.partid, P.partname, PES.qty, PES.unit
FROM (SELECT partid, unit, SUM(qty) AS qty
      FROM dbo.PartsExplosion(2) AS PE
      GROUP BY partid, unit) AS PES
  JOIN dbo.Parts AS P
    ON P.partid = PES.partid;
GO

SELECT P.partid, P.partname, PES.qty, PES.unit
FROM (SELECT partid, unit, SUM(qty) AS qty
      FROM dbo.PartsExplosion(5) AS PE
      GROUP BY partid, unit) AS PES
  JOIN dbo.Parts AS P
    ON P.partid = PES.partid;
GO

-- Creation Script for Function Subordinates2

---------------------------------------------------------------------
-- Function: Subordinates2,
--           Descendants with optional level limit
--
-- Input   : @root      INT: Manager id
--           @maxlevels INT: Max number of levels to return
--
-- Output  : @Subs TABLE: id and level of subordinates of
--                        input manager in all levels <= @maxlevels
--
-- Process : * Insert into @Subs row of input manager
--           * In a loop, while previous insert loaded more than 0 rows
--             and previous level is smaller than @maxlevels
--             insert into @Subs next level of subordinates
---------------------------------------------------------------------
USE tempdb;
GO
IF OBJECT_ID('dbo.Subordinates2') IS NOT NULL
  DROP FUNCTION dbo.Subordinates2;
GO
CREATE FUNCTION dbo.Subordinates2
  (@root AS INT, @maxlevels AS INT = NULL) RETURNS @Subs TABLE
(
  empid INT NOT NULL PRIMARY KEY NONCLUSTERED,
  lvl   INT NOT NULL,
  UNIQUE CLUSTERED(lvl, empid)  -- Index will be used to filter level
)
AS
BEGIN
  DECLARE @lvl AS INT = 0;      -- Initialize level counter with 0
  -- If input @maxlevels is NULL, set it to maximum integer
  -- to virtually have no limit on levels
  SET @maxlevels = COALESCE(@maxlevels, 2147483647);

  -- Insert root node to @Subs
  INSERT INTO @Subs(empid, lvl)
    SELECT empid, @lvl FROM dbo.Employees WHERE empid = @root;

  WHILE @@rowcount > 0          -- while previous level had rows
    AND @lvl < @maxlevels       -- and previous level < @maxlevels
  BEGIN
    SET @lvl = @lvl + 1;        -- Increment level counter

    -- Insert next level of subordinates to @Subs
    INSERT INTO @Subs(empid, lvl)
      SELECT C.empid, @lvl
      FROM @Subs AS P           -- P = Parent
        JOIN dbo.Employees AS C -- C = Child
          ON P.lvl = @lvl - 1   -- Filter parents from previous level
          AND C.mgrid = P.empid;
  END

  RETURN;
END
GO

-- Descendants of a given node, no limit on levels
SELECT empid, lvl
FROM dbo.Subordinates2(3, NULL) AS S;

-- Descendants of a given node, limit 2 levels
SELECT empid, lvl
FROM dbo.Subordinates2(3, 2) AS S;

-- Descendants that are 2 levels underneath a given node 返回员工3以下第二级下属
SELECT empid
FROM dbo.Subordinates2(3, 2) AS S
WHERE lvl = 2;
GO

-- Subtree with level limit, CTE Solution, with MAXRECURSION

DECLARE @root AS INT = 3;

WITH Subs
AS
(
  SELECT empid, empname, 0 AS lvl
  FROM dbo.Employees
  WHERE empid = @root

  UNION ALL

  SELECT C.empid, C.empname, P.lvl + 1
  FROM Subs AS P
    JOIN dbo.Employees AS C
      ON C.mgrid = P.empid
)
SELECT * FROM Subs
OPTION (MAXRECURSION 2);
GO

-- Subtree with level limit, CTE Solution, with level column
DECLARE @root AS INT = 3, @maxlevels AS INT = 2;

WITH Subs
AS
(
  SELECT empid, empname, 0 AS lvl
  FROM dbo.Employees
  WHERE empid = @root

  UNION ALL

  SELECT C.empid, C.empname, P.lvl + 1
  FROM Subs AS P
    JOIN dbo.Employees AS C
      ON C.mgrid = P.empid
)
SELECT * FROM Subs
WHERE lvl <= @maxlevels;

---------------------------------------------------------------------
-- Sub-Path
---------------------------------------------------------------------

-- Creation Script for Function Managers 

---------------------------------------------------------------------
-- Function: Managers, Ancestors with optional level limit 具有可选级数限制的祖先（父）
--
-- Input   : @empid INT : Employee id
--           @maxlevels : Max number of levels to return
--
-- Output  : @Mgrs Table: id and level of managers of
--                        input employee in all levels <= @maxlevels
--
-- Process : * In a loop, while current manager is not null
--             and previous level is smaller than @maxlevels
--             insert into @Mgrs current manager,
--             and get next level manager
---------------------------------------------------------------------
USE tempdb;
GO
IF OBJECT_ID('dbo.Managers') IS NOT NULL
  DROP FUNCTION dbo.Managers;
GO
CREATE FUNCTION dbo.Managers
  (@empid AS INT, @maxlevels AS INT = NULL) RETURNS @Mgrs TABLE
(
  empid INT NOT NULL PRIMARY KEY,
  lvl   INT NOT NULL
)
AS
BEGIN
  IF NOT EXISTS(SELECT * FROM dbo.Employees WHERE empid = @empid)
    RETURN;  

  DECLARE @lvl AS INT = 0;      -- Initialize level counter with 0
  -- If input @maxlevels is NULL, set it to maximum integer
  -- to virtually have no limit on levels
  SET @maxlevels = COALESCE(@maxlevels, 2147483647);

  WHILE @empid IS NOT NULL      -- while current employee has a manager
    AND @lvl <= @maxlevels      -- and previous level <= @maxlevels
  BEGIN
    -- Insert current manager to @Mgrs
    INSERT INTO @Mgrs(empid, lvl) VALUES(@empid, @lvl);
    SET @lvl = @lvl + 1;        -- Increment level counter
    -- Get next level manager
    SET @empid = (SELECT mgrid FROM dbo.Employees WHERE empid = @empid);
  END

  RETURN;
END
GO

-- Ancestors of a given node, no limit on levels 返回员工8的所有级别的经理
SELECT empid, lvl
FROM dbo.Managers(8, NULL) AS M;

-- Ancestors of a Given Node, CTE Solution

-- Ancestors of a given node, CTE Solution
DECLARE @empid AS INT = 8;

WITH Mgrs
AS
(
  SELECT empid, mgrid, empname, 0 AS lvl
  FROM dbo.Employees
  WHERE empid = @empid

  UNION ALL

  SELECT P.empid, P.mgrid, P.empname, C.lvl + 1
  FROM Mgrs AS C
    JOIN dbo.Employees AS P
      ON C.mgrid = P.empid
)
SELECT * FROM Mgrs;

-- Ancestors of a given node, limit 2 levels
SELECT empid, lvl
FROM dbo.Managers(8, 2) AS M;
GO

-- Ancestors with Level Limit, CTE Solution
DECLARE @empid AS INT = 8, @maxlevels AS INT = 2;

WITH Mgrs
AS
(
  SELECT empid, mgrid, empname, 0 AS lvl
  FROM dbo.Employees
  WHERE empid = @empid

  UNION ALL

  SELECT P.empid, P.mgrid, P.empname, C.lvl + 1
  FROM Mgrs AS C
    JOIN dbo.Employees AS P
      ON C.mgrid = P.empid
)
SELECT * FROM Mgrs
WHERE lvl <= @maxlevels;

-- Ancestor that is 2 levels above a given node
SELECT empid
FROM dbo.Managers(8, 2) AS M
WHERE lvl = 2;
GO

---------------------------------------------------------------------
-- Subtree/Subgraph with Path Enumeration 带有路径枚举的子图/子树
---------------------------------------------------------------------

-- Creation Script for Function Subordinates3

---------------------------------------------------------------------
-- Function: Subordinates3,
--           Descendants with optional level limit,具有可选级数的下属，以及路径枚举
--           and path enumeration
--
-- Input   : @root      INT: Manager id
--           @maxlevels INT: Max number of levels to return
--
-- Output  : @Subs TABLE: id, level and materialized ancestors path
--                        of subordinates of input manager
--                        in all levels <= @maxlevels
--
-- Process : * Insert into @Subs row of input manager
--           * In a loop, while previous insert loaded more than 0 rows
--             and previous level is smaller than @maxlevels:
--             - insert into @Subs next level of subordinates
--             - calculate a materialized ancestors path for each
--               by concatenating current node id to parent's path
---------------------------------------------------------------------
USE tempdb;
GO
IF OBJECT_ID('dbo.Subordinates3') IS NOT NULL
  DROP FUNCTION dbo.Subordinates3;
GO
CREATE FUNCTION dbo.Subordinates3
  (@root AS INT, @maxlevels AS INT = NULL) RETURNS @Subs TABLE
(
  empid INT          NOT NULL PRIMARY KEY NONCLUSTERED,
  lvl   INT          NOT NULL,
  path  VARCHAR(900) NOT NULL
  UNIQUE CLUSTERED(lvl, empid)  -- Index will be used to filter level
)
AS
BEGIN
  DECLARE @lvl AS INT = 0;      -- Initialize level counter with 0
  -- If input @maxlevels is NULL, set it to maximum integer
  -- to virtually have no limit on levels
  SET @maxlevels = COALESCE(@maxlevels, 2147483647);

  -- Insert root node to @Subs
  INSERT INTO @Subs(empid, lvl, path)
    SELECT empid, @lvl, '.' + CAST(empid AS VARCHAR(10)) + '.'
    FROM dbo.Employees WHERE empid = @root;

  WHILE @@rowcount > 0          -- while previous level had rows
    AND @lvl < @maxlevels       -- and previous level < @maxlevels
  BEGIN
    SET @lvl = @lvl + 1;        -- Increment level counter

    -- Insert next level of subordinates to @Subs
    INSERT INTO @Subs(empid, lvl, path)
      SELECT C.empid, @lvl,
        P.path + CAST(C.empid AS VARCHAR(10)) + '.'
      FROM @Subs AS P           -- P = Parent
        JOIN dbo.Employees AS C -- C = Child
          ON P.lvl = @lvl - 1   -- Filter parents from previous level
          AND C.mgrid = P.empid;
  END

  RETURN;
END
GO

-- Return descendants of a given node, along with a materialized path
SELECT empid, lvl, path
FROM dbo.Subordinates3(1, NULL) AS S;

-- Return descendants of a given node, sorted and indented
SELECT E.empid, REPLICATE(' | ', lvl) + empname AS empname
FROM dbo.Subordinates3(1, NULL) AS S
  JOIN dbo.Employees AS E
    ON E.empid = S.empid
ORDER BY path;

-- Subtree with Path Enumeration, CTE Solution

-- Descendants of a given node, with Materialized Path, CTE Solution
DECLARE @root AS INT = 1;

WITH Subs
AS
(
  SELECT empid, empname, 0 AS lvl,
    -- Path of root = '.' + empid + '.'
    CAST('.' + CAST(empid AS VARCHAR(10)) + '.'
         AS VARCHAR(MAX)) AS path
  FROM dbo.Employees
  WHERE empid = @root

  UNION ALL

  SELECT C.empid, C.empname, P.lvl + 1,
    -- Path of child = parent's path + child empid + '.'
    CAST(P.path + CAST(C.empid AS VARCHAR(10)) + '.'
         AS VARCHAR(MAX))
  FROM Subs AS P
    JOIN dbo.Employees AS C
      ON C.mgrid = P.empid
)
SELECT empid, REPLICATE(' | ', lvl) + empname AS empname
FROM Subs
ORDER BY path;

---------------------------------------------------------------------
-- Sorting
---------------------------------------------------------------------

-- Sorting Hierarchy by empname, CTE Solution
DECLARE @root AS INT = 1;

WITH Subs
AS
(
  SELECT empid, empname, 0 AS lvl,
    -- Path of root is 1 (binary)
    CAST(1 AS VARBINARY(MAX)) AS sort_path
  FROM dbo.Employees
  WHERE empid = @root

  UNION ALL

  SELECT C.empid, C.empname, P.lvl + 1,
    -- Path of child = parent's path + child row number (binary)
    P.sort_path + CAST(
      ROW_NUMBER() OVER(PARTITION BY C.mgrid
                        ORDER BY C.empname) -- sort col(s)
      AS BINARY(4))
  FROM Subs AS P
    JOIN dbo.Employees AS C
      ON C.mgrid = P.empid
)
SELECT empid, ROW_NUMBER() OVER(ORDER BY sort_path) AS sortval,
  REPLICATE(' | ', lvl) + empname AS empname
FROM Subs
ORDER BY sortval;
GO

-- Sorting Hierarchy by salary, CTE Solution
DECLARE @root AS INT = 1;

WITH Subs
AS
(
  SELECT empid, empname, salary, 0 AS lvl,
    -- Path of root = 1 (binary)
    CAST(1 AS VARBINARY(MAX)) AS sort_path
  FROM dbo.Employees
  WHERE empid = @root

  UNION ALL

  SELECT C.empid, C.empname, C.salary, P.lvl + 1,
    -- Path of child = parent's path + child row number (binary)
    P.sort_path + CAST(
      ROW_NUMBER() OVER(PARTITION BY C.mgrid
                        ORDER BY C.salary) -- sort col(s)
      AS BINARY(4))
  FROM Subs AS P
    JOIN dbo.Employees AS C
      ON C.mgrid = P.empid
)
SELECT empid, salary, ROW_NUMBER() OVER(ORDER BY sort_path) AS sortval,
  REPLICATE(' | ', lvl) + empname AS empname
FROM Subs
ORDER BY sortval;

---------------------------------------------------------------------
-- Cycles 环
---------------------------------------------------------------------

-- Create a cyclic path
UPDATE dbo.Employees SET mgrid = 14 WHERE empid = 1;
GO

-- Detecting Cycles, CTE Solution
DECLARE @root AS INT = 1;

WITH Subs
AS
(
  SELECT empid, empname, 0 AS lvl,
    CAST('.' + CAST(empid AS VARCHAR(10)) + '.'
         AS VARCHAR(MAX)) AS path,
    -- Obviously root has no cycle
    0 AS cycle
  FROM dbo.Employees
  WHERE empid = @root

  UNION ALL

  SELECT C.empid, C.empname, P.lvl + 1,
    CAST(P.path + CAST(C.empid AS VARCHAR(10)) + '.'
         AS VARCHAR(MAX)),
    -- Cycle detected if parent's path contains child's id
    CASE WHEN P.path LIKE '%.' + CAST(C.empid AS VARCHAR(10)) + '.%'
      THEN 1 ELSE 0 END
  FROM Subs AS P
    JOIN dbo.Employees AS C
      ON C.mgrid = P.empid
)
SELECT empid, empname, cycle, path
FROM Subs;
GO

-- Not Pursuing Cycles, CTE Solution
DECLARE @root AS INT = 1;

WITH Subs
AS
(
  SELECT empid, empname, 0 AS lvl,
    CAST('.' + CAST(empid AS VARCHAR(10)) + '.'
         AS VARCHAR(MAX)) AS path,
    -- Obviously root has no cycle
    0 AS cycle
  FROM dbo.Employees
  WHERE empid = @root

  UNION ALL

  SELECT C.empid, C.empname, P.lvl + 1,
    CAST(P.path + CAST(C.empid AS VARCHAR(10)) + '.'
         AS VARCHAR(MAX)),
    -- Cycle detected if parent's path contains child's id
    CASE WHEN P.path LIKE '%.' + CAST(C.empid AS VARCHAR(10)) + '.%'
      THEN 1 ELSE 0 END
  FROM Subs AS P
    JOIN dbo.Employees AS C
      ON C.mgrid = P.empid
      AND P.cycle = 0 -- do not pursue branch for parent with cycle
)
SELECT empid, empname, cycle, path
FROM Subs;
GO

-- Isolating Cyclic Paths, CTE Solution
DECLARE @root AS INT = 1;

WITH Subs
AS
(
  SELECT empid, empname, 0 AS lvl,
    CAST('.' + CAST(empid AS VARCHAR(10)) + '.'
         AS VARCHAR(MAX)) AS path,
    -- Obviously root has no cycle
    0 AS cycle
  FROM dbo.Employees
  WHERE empid = @root

  UNION ALL

  SELECT C.empid, C.empname, P.lvl + 1,
    CAST(P.path + CAST(C.empid AS VARCHAR(10)) + '.'
         AS VARCHAR(MAX)),
    -- Cycle detected if parent's path contains child's id
    CASE WHEN P.path LIKE '%.' + CAST(C.empid AS VARCHAR(10)) + '.%'
      THEN 1 ELSE 0 END
  FROM Subs AS P
    JOIN dbo.Employees AS C
      ON C.mgrid = P.empid
      AND P.cycle = 0
)
SELECT path FROM Subs WHERE cycle = 1;

-- Fix cyclic path
UPDATE dbo.Employees SET mgrid = NULL WHERE empid = 1;

---------------------------------------------------------------------
-- Materialized Path
---------------------------------------------------------------------

---------------------------------------------------------------------
-- Custom Materialized Path
---------------------------------------------------------------------

---------------------------------------------------------------------
-- Maintaining Data
---------------------------------------------------------------------

-- DDL for Employees with Path
SET NOCOUNT ON;
USE tempdb;
GO
IF OBJECT_ID('dbo.Employees') IS NOT NULL
  DROP TABLE dbo.Employees;
GO
CREATE TABLE dbo.Employees
(
  empid   INT          NOT NULL PRIMARY KEY NONCLUSTERED,
  mgrid   INT          NULL     REFERENCES dbo.Employees,
  empname VARCHAR(25)  NOT NULL,
  salary  MONEY        NOT NULL,
  lvl     INT          NOT NULL,
  path    VARCHAR(900) NOT NULL UNIQUE CLUSTERED
);
CREATE UNIQUE INDEX idx_unc_mgrid_empid ON dbo.Employees(mgrid, empid);
GO

---------------------------------------------------------------------
-- Adding Employees who Manage No One (Leaves) 具体化路径
---------------------------------------------------------------------

-- Creation Script for Procedure AddEmp

---------------------------------------------------------------------
-- Stored Procedure: AddEmp,
--   Inserts new employee who manages no one into the table
---------------------------------------------------------------------
USE tempdb;
GO
IF OBJECT_ID('dbo.AddEmp') IS NOT NULL
  DROP PROC dbo.AddEmp;
GO
CREATE PROC dbo.AddEmp
  @empid   INT,
  @mgrid   INT,
  @empname VARCHAR(25),
  @salary  MONEY
AS

SET NOCOUNT ON;

-- Handle case where the new employee has no manager (root)
IF @mgrid IS NULL
  INSERT INTO dbo.Employees(empid, mgrid, empname, salary, lvl, path)
    VALUES(@empid, @mgrid, @empname, @salary,
      0, '.' + CAST(@empid AS VARCHAR(10)) + '.');
-- Handle subordinate case (non-root)
ELSE
  INSERT INTO dbo.Employees(empid, mgrid, empname, salary, lvl, path)
    SELECT @empid, @mgrid, @empname, @salary,
      lvl + 1, path + CAST(@empid AS VARCHAR(10)) + '.'
    FROM dbo.Employees
    WHERE empid = @mgrid;
GO

-- Sample Data for Employees with Path
EXEC dbo.AddEmp
  @empid = 1, @mgrid = NULL, @empname = 'David', @salary = $10000.00;
EXEC dbo.AddEmp
  @empid = 2, @mgrid = 1, @empname = 'Eitan', @salary = $7000.00;
EXEC dbo.AddEmp
  @empid = 3, @mgrid = 1, @empname = 'Ina', @salary = $7500.00;
EXEC dbo.AddEmp
  @empid = 4, @mgrid = 2, @empname = 'Seraph', @salary = $5000.00;
EXEC dbo.AddEmp
  @empid = 5, @mgrid = 2, @empname = 'Jiru', @salary = $5500.00;
EXEC dbo.AddEmp
  @empid = 6, @mgrid = 2, @empname = 'Steve', @salary = $4500.00;
EXEC dbo.AddEmp
  @empid = 7, @mgrid = 3, @empname = 'Aaron', @salary = $5000.00;
EXEC dbo.AddEmp
  @empid = 8, @mgrid = 5, @empname = 'Lilach', @salary = $3500.00;
EXEC dbo.AddEmp
  @empid = 9, @mgrid = 7, @empname = 'Rita', @salary = $3000.00;
EXEC dbo.AddEmp
  @empid = 10, @mgrid = 5, @empname = 'Sean', @salary = $3000.00;
EXEC dbo.AddEmp
  @empid = 11, @mgrid = 7, @empname = 'Gabriel', @salary = $3000.00;
EXEC dbo.AddEmp
  @empid = 12, @mgrid = 9, @empname = 'Emilia', @salary = $2000.00;
EXEC dbo.AddEmp
  @empid = 13, @mgrid = 9, @empname = 'Michael', @salary = $2000.00;
EXEC dbo.AddEmp
  @empid = 14, @mgrid = 9, @empname = 'Didi', @salary = $1500.00;
GO

-- Examine data after load
SELECT empid, mgrid, empname, salary, lvl, path
FROM dbo.Employees
ORDER BY path;

---------------------------------------------------------------------
-- Moving a Subtree
---------------------------------------------------------------------

-- Creation Script for Procedure MoveSubtree

---------------------------------------------------------------------
-- Stored Procedure: MoveSubtree,
--   Moves a whole subtree of a given root to a new location
--   under a given manager
---------------------------------------------------------------------
USE tempdb;
GO
IF OBJECT_ID('dbo.MoveSubtree') IS NOT NULL
  DROP PROC dbo.MoveSubtree;
GO
CREATE PROC dbo.MoveSubtree
  @root  INT,
  @mgrid INT
AS

SET NOCOUNT ON;

BEGIN TRAN;
  -- Update level and path of all employees in the subtree (E)
  -- Set level =
  --   current level + new manager's level - old manager's level
  -- Set path =
  --   in current path remove old manager's path
  --   and substitute with new manager's path
  UPDATE E
    SET lvl  = E.lvl + NM.lvl - OM.lvl,
        path = STUFF(E.path, 1, LEN(OM.path), NM.path)
  FROM dbo.Employees AS E          -- E = Employees    (subtree)
    JOIN dbo.Employees AS R        -- R = Root         (one row)
      ON R.empid = @root
      AND E.path LIKE R.path + '%'
    JOIN dbo.Employees AS OM       -- OM = Old Manager (one row)
      ON OM.empid = R.mgrid
    JOIN dbo.Employees AS NM       -- NM = New Manager (one row)
      ON NM.empid = @mgrid;

  -- Update root's new manager
  UPDATE dbo.Employees SET mgrid = @mgrid WHERE empid = @root;
COMMIT TRAN;
GO

-- Before moving subtree
SELECT empid, REPLICATE(' | ', lvl) + empname AS empname, lvl, path
FROM dbo.Employees
ORDER BY path;

-- Move Subtree 移动子树
BEGIN TRAN;

  EXEC dbo.MoveSubtree
  @root  = 7,
  @mgrid = 10;

  -- After moving subtree
  SELECT empid, REPLICATE(' | ', lvl) + empname AS empname, lvl, path
  FROM dbo.Employees
  ORDER BY path;

ROLLBACK TRAN; -- rollback used in order not to apply the change

---------------------------------------------------------------------
-- Removing a Subtree
---------------------------------------------------------------------

-- Before deleteting subtree
SELECT empid, REPLICATE(' | ', lvl) + empname AS empname, lvl, path
FROM dbo.Employees
ORDER BY path;

-- Delete Subtree  删除子树
BEGIN TRAN;

  DELETE FROM dbo.Employees
  WHERE path LIKE
    (SELECT M.path + '%'
     FROM dbo.Employees as M
     WHERE M.empid = 7);

  -- After deleting subtree
  SELECT empid, REPLICATE(' | ', lvl) + empname AS empname, lvl, path
  FROM dbo.Employees
  ORDER BY path;

ROLLBACK TRAN; -- rollback used in order not to apply the change

---------------------------------------------------------------------
-- Querying Materialized Path 查询
---------------------------------------------------------------------

-- Subtree of a given root
SELECT REPLICATE(' | ', E.lvl - M.lvl) + E.empname
FROM dbo.Employees AS E
  JOIN dbo.Employees AS M
    ON M.empid = 3 -- root
    AND E.path LIKE M.path + '%'
ORDER BY E.path;

-- Subtree of a given root, excluding root
SELECT REPLICATE(' | ', E.lvl - M.lvl - 1) + E.empname
FROM dbo.Employees AS E
  JOIN dbo.Employees AS M
    ON M.empid = 3
    AND E.path LIKE M.path + '_%'
ORDER BY E.path;

-- Leaf nodes under a given root
SELECT E.empid, E.empname
FROM dbo.Employees AS E
  JOIN dbo.Employees AS M
    ON M.empid = 3
    AND E.path LIKE M.path + '%'
WHERE NOT EXISTS
  (SELECT *
   FROM dbo.Employees AS E2
   WHERE E2.mgrid = E.empid);

-- Subtree of a given root, limit number of levels
SELECT REPLICATE(' | ', E.lvl - M.lvl) + E.empname
FROM dbo.Employees AS E
  JOIN dbo.Employees AS M
    ON M.empid = 3
    AND E.path LIKE M.path + '%'
    AND E.lvl - M.lvl <= 2
ORDER BY E.path;

-- Nodes that are n levels under a given root
SELECT E.empid, E.empname
FROM dbo.Employees AS E
  JOIN dbo.Employees AS M
    ON M.empid = 3
    AND E.path LIKE M.path + '%'
    AND E.lvl - M.lvl = 2;

-- Ancestors of a given node (requires a table scan)
SELECT REPLICATE(' | ', M.lvl) + M.empname
FROM dbo.Employees AS E
  JOIN dbo.Employees AS M
    ON E.empid = 14
    AND E.path LIKE M.path + '%'
ORDER BY E.path;

-- Creating and Populating Auxiliary Table of Numbers
SET NOCOUNT ON;
USE tempdb;
GO
IF OBJECT_ID('dbo.Nums') IS NOT NULL
  DROP TABLE dbo.Nums;
GO
CREATE TABLE dbo.Nums(n INT NOT NULL PRIMARY KEY);
DECLARE @max AS INT = 1000000, @rc AS INT = 1;

INSERT INTO Nums VALUES(1);
WHILE @rc * 2 <= @max
BEGIN
  INSERT INTO dbo.Nums SELECT n + @rc FROM dbo.Nums;
  SET @rc = @rc * 2;
END

INSERT INTO dbo.Nums
  SELECT n + @rc FROM dbo.Nums WHERE n + @rc <= @max;
GO

-- Creation Script for Function SplitPath
USE tempdb;
GO
IF OBJECT_ID('dbo.SplitPath') IS NOT NULL
  DROP FUNCTION dbo.SplitPath;
GO
CREATE FUNCTION dbo.SplitPath(@empid AS INT) RETURNS TABLE
AS
RETURN
  SELECT
    ROW_NUMBER() OVER(ORDER BY n) AS pos,
    CAST(SUBSTRING(path, n + 1,
           CHARINDEX('.', path, n + 1) - n - 1) AS INT) AS empid
  FROM dbo.Employees
    JOIN dbo.Nums
      ON empid = @empid
      AND n < LEN(path)
      AND SUBSTRING(path, n, 1) = '.';
GO

-- Test SplitPath function
SELECT pos, empid FROM dbo.SplitPath(14);

-- Getting ancestors using SplitPath function
SELECT REPLICATE(' | ', lvl) + empname
FROM dbo.SplitPath(14) AS SP
  JOIN dbo.Employees AS E
    ON E.empid = SP.empid
ORDER BY path;

-- Presentation
SELECT REPLICATE(' | ', lvl) + empname
FROM dbo.Employees
ORDER BY path;

---------------------------------------------------------------------
-- Materialized Path with the HIERARCHYID Datatype 使用HIERARCHYID数据类型的具体化路径
--HIERARCHYID类型提供了下列方法和属性：GetLevel,GetRoot,GetAncestor,GetDescendant,GetReparentedValue,IsDescendantOf,ToString,Parse,Read,Write
---------------------------------------------------------------------

SET NOCOUNT ON;
USE tempdb;
GO
IF OBJECT_ID('dbo.Employees') IS NOT NULL
  DROP TABLE dbo.Employees;
GO
CREATE TABLE dbo.Employees
(
  empid   INT NOT NULL,
  hid     HIERARCHYID NOT NULL,
  lvl AS hid.GetLevel() PERSISTED,
  empname VARCHAR(25) NOT NULL,
  salary  MONEY       NOT NULL,
  mgrid INT NULL
);

CREATE UNIQUE CLUSTERED INDEX idx_depth_first ON dbo.Employees(hid);
CREATE UNIQUE INDEX idx_breadth_first ON dbo.Employees(lvl, hid);
CREATE UNIQUE INDEX idx_empid ON dbo.Employees(empid);
GO

---------------------------------------------------------------------
-- Maintaining Data
---------------------------------------------------------------------

---------------------------------------------------------------------
-- Adding Employees
---------------------------------------------------------------------

---------------------------------------------------------------------
-- Stored Procedure: AddEmp,
--   Inserts new employee who manages no one into the table
---------------------------------------------------------------------
IF OBJECT_ID('dbo.AddEmp', 'P') IS NOT NULL
  DROP PROC dbo.AddEmp;
GO
CREATE PROC dbo.AddEmp
  @empid   AS INT,
  @mgrid   AS INT,
  @empname AS VARCHAR(25),
  @salary  AS MONEY
AS

DECLARE
  @hid            AS HIERARCHYID,
  @mgr_hid        AS HIERARCHYID,
  @last_child_hid AS HIERARCHYID;

BEGIN TRAN

  IF @mgrid IS NULL
    SET @hid = hierarchyid::GetRoot();
  ELSE
  BEGIN
    SET @mgr_hid = (SELECT hid FROM dbo.Employees WITH (UPDLOCK)
                    WHERE empid = @mgrid);
    SET @last_child_hid =
      (SELECT MAX(hid) FROM dbo.Employees
       WHERE hid.GetAncestor(1) = @mgr_hid);
    SET @hid = @mgr_hid.GetDescendant(@last_child_hid, NULL);
  END

  INSERT INTO dbo.Employees(empid, hid, empname, salary)
    VALUES(@empid, @hid, @empname, @salary);

COMMIT TRAN
GO

EXEC dbo.AddEmp @empid =  1, @mgrid = NULL, @empname = 'David'  , @salary = $10000.00;
EXEC dbo.AddEmp @empid =  2, @mgrid =    1, @empname = 'Eitan'  , @salary = $7000.00;
EXEC dbo.AddEmp @empid =  3, @mgrid =    1, @empname = 'Ina'    , @salary = $7500.00;
EXEC dbo.AddEmp @empid =  4, @mgrid =    2, @empname = 'Seraph' , @salary = $5000.00;
EXEC dbo.AddEmp @empid =  5, @mgrid =    2, @empname = 'Jiru'   , @salary = $5500.00;
EXEC dbo.AddEmp @empid =  6, @mgrid =    2, @empname = 'Steve'  , @salary = $4500.00;
EXEC dbo.AddEmp @empid =  7, @mgrid =    3, @empname = 'Aaron'  , @salary = $5000.00;
EXEC dbo.AddEmp @empid =  8, @mgrid =    5, @empname = 'Lilach' , @salary = $3500.00;
EXEC dbo.AddEmp @empid =  9, @mgrid =    7, @empname = 'Rita'   , @salary = $3000.00;
EXEC dbo.AddEmp @empid = 10, @mgrid =    5, @empname = 'Sean'   , @salary = $3000.00;
EXEC dbo.AddEmp @empid = 11, @mgrid =    7, @empname = 'Gabriel', @salary = $3000.00;
EXEC dbo.AddEmp @empid = 12, @mgrid =    9, @empname = 'Emilia' , @salary = $2000.00;
EXEC dbo.AddEmp @empid = 13, @mgrid =    9, @empname = 'Michael', @salary = $2000.00;
EXEC dbo.AddEmp @empid = 14, @mgrid =    9, @empname = 'Didi'   , @salary = $1500.00;
GO

SELECT hid, hid.ToString() AS path, lvl, empid, empname, salary
FROM dbo.Employees
ORDER BY hid;

SELECT *
FROM dbo.Employees
---------------------------------------------------------------------
-- Moving a Subtree
---------------------------------------------------------------------

SELECT
  CAST('/1/1/2/3/2/' AS HIERARCHYID).GetReparentedValue('/1/1/', '/2/1/4/').ToString();

---------------------------------------------------------------------
-- Stored Procedure: MoveSubtree, 移动子树
--   Moves a whole subtree of a given root to a new location
--   under a given manager
---------------------------------------------------------------------
IF OBJECT_ID('dbo.MoveSubtree') IS NOT NULL
  DROP PROC dbo.MoveSubtree;
GO
CREATE PROC dbo.MoveSubtree
  @empid    AS INT,
  @new_mgrid AS INT
AS

DECLARE
  @old_root AS HIERARCHYID,
  @new_root AS HIERARCHYID,
  @new_mgr_hid AS HIERARCHYID;

BEGIN TRAN

  SET @new_mgr_hid = (SELECT hid FROM dbo.Employees WITH (UPDLOCK)
                      WHERE empid = @new_mgrid);
  SET @old_root = (SELECT hid FROM dbo.Employees
                   WHERE empid = @empid);

  -- First, get a new hid for the subtree root employee that moves
  SET @new_root = @new_mgr_hid.GetDescendant
    ((SELECT MAX(hid)
      FROM dbo.Employees
      WHERE hid.GetAncestor(1) = @new_mgr_hid),
     NULL);

  -- Next, reparent all descendants of employee that moves
  UPDATE dbo.Employees
    SET hid = hid.GetReparentedValue(@old_root, @new_root)
  WHERE hid.IsDescendantOf(@old_root) = 1;

COMMIT TRAN
GO

SELECT empid, REPLICATE(' | ', lvl) + empname AS empname, hid.ToString() AS path
FROM dbo.Employees
ORDER BY hid;

BEGIN TRAN

  EXEC dbo.MoveSubtree
    @empid    = 5,
    @new_mgrid = 9;

  SELECT empid, REPLICATE(' | ', lvl) + empname AS empname, hid.ToString() AS path
  FROM dbo.Employees
  ORDER BY hid;

ROLLBACK TRAN
GO

---------------------------------------------------------------------
-- Querying 查询
---------------------------------------------------------------------

-- Subtree
SELECT E.empid, E.empname
FROM dbo.Employees AS M
  JOIN dbo.Employees AS E
    ON M.empid = 3
    AND E.hid.IsDescendantOf(M.hid) = 1
WHERE E.lvl - M.lvl <= 3;

-- Path 路径
SELECT M.empid, M.empname
FROM dbo.Employees AS M
  JOIN dbo.Employees AS E
    ON E.empid = 14
    AND E.hid.IsDescendantOf(M.hid) = 1;

-- Direct Subordinates 直接下属
SELECT E.empid, E.empname
FROM dbo.Employees AS M
  JOIN dbo.Employees AS E
    ON M.empid = 2
    AND E.hid.GetAncestor(1) = M.hid;

-- Leaf nodes 叶子节点
SELECT empid, empname
FROM dbo.Employees AS M
WHERE NOT EXISTS
  (SELECT * FROM dbo.Employees AS E
   WHERE E.hid.GetAncestor(1) = M.hid);

-- Presentation/sorting
SELECT REPLICATE(' | ', lvl) + empname AS empname, hid.ToString() AS path
FROM dbo.Employees
ORDER BY hid;

---------------------------------------------------------------------
-- Further Aspects of Working with HIERARCHYID
---------------------------------------------------------------------

---------------------------------------------------------------------
-- Normalizing HIERARCHYID Values
---------------------------------------------------------------------

---------------------------------------------------------------------
-- Stored Procedure: AddEmp,
--   Inserts new employee who manages no one into the table
---------------------------------------------------------------------
IF OBJECT_ID('dbo.AddEmp', 'P') IS NOT NULL
  DROP PROC dbo.AddEmp;
GO
CREATE PROC dbo.AddEmp
  @empid      AS INT,
  @mgrid      AS INT,
  @leftempid  AS INT,
  @rightempid AS INT,
  @empname    AS VARCHAR(25),
  @salary     AS MONEY = 1000
AS

DECLARE @hid AS HIERARCHYID;

IF @mgrid IS NULL
  SET @hid = hierarchyid::GetRoot();
ELSE
  SET @hid = (SELECT hid FROM dbo.Employees WHERE empid = @mgrid).GetDescendant
    ( (SELECT hid FROM dbo.Employees WHERE empid = @leftempid),
      (SELECT hid FROM dbo.Employees WHERE empid = @rightempid) );

INSERT INTO dbo.Employees(empid, hid, empname, salary)
  VALUES(@empid, @hid, @empname, @salary);
GO

TRUNCATE TABLE dbo.Employees;

EXEC dbo.AddEmp @empid =  1, @mgrid = NULL, @leftempid = NULL, @rightempid = NULL, @empname = 'A';
EXEC dbo.AddEmp @empid =  2, @mgrid =    1, @leftempid = NULL, @rightempid = NULL, @empname = 'B';
EXEC dbo.AddEmp @empid =  3, @mgrid =    1, @leftempid =    2, @rightempid = NULL, @empname = 'C';
EXEC dbo.AddEmp @empid =  4, @mgrid =    1, @leftempid =    2, @rightempid =    3, @empname = 'D';
EXEC dbo.AddEmp @empid =  5, @mgrid =    1, @leftempid =    4, @rightempid =    3, @empname = 'E';
EXEC dbo.AddEmp @empid =  6, @mgrid =    1, @leftempid =    4, @rightempid =    5, @empname = 'F';
EXEC dbo.AddEmp @empid =  7, @mgrid =    1, @leftempid =    6, @rightempid =    5, @empname = 'G';
EXEC dbo.AddEmp @empid =  8, @mgrid =    1, @leftempid =    6, @rightempid =    7, @empname = 'H';
EXEC dbo.AddEmp @empid =  9, @mgrid =    8, @leftempid = NULL, @rightempid = NULL, @empname = 'I';
EXEC dbo.AddEmp @empid = 10, @mgrid =    8, @leftempid =    9, @rightempid = NULL, @empname = 'J';
EXEC dbo.AddEmp @empid = 11, @mgrid =    8, @leftempid =    9, @rightempid =   10, @empname = 'K';
EXEC dbo.AddEmp @empid = 12, @mgrid =    8, @leftempid =   11, @rightempid =   10, @empname = 'J';
EXEC dbo.AddEmp @empid = 13, @mgrid =    8, @leftempid =   11, @rightempid =   12, @empname = 'L';
EXEC dbo.AddEmp @empid = 14, @mgrid =    8, @leftempid =   13, @rightempid =   12, @empname = 'M';
EXEC dbo.AddEmp @empid = 15, @mgrid =    8, @leftempid =   13, @rightempid =   14, @empname = 'N';
EXEC dbo.AddEmp @empid = 16, @mgrid =    8, @leftempid =   15, @rightempid =   14, @empname = 'O';
EXEC dbo.AddEmp @empid = 17, @mgrid =    8, @leftempid =   15, @rightempid =   16, @empname = 'P';
EXEC dbo.AddEmp @empid = 18, @mgrid =    8, @leftempid =   17, @rightempid =   16, @empname = 'Q';
EXEC dbo.AddEmp @empid = 19, @mgrid =    8, @leftempid =   17, @rightempid =   18, @empname = 'E';
EXEC dbo.AddEmp @empid = 20, @mgrid =    8, @leftempid =   19, @rightempid =   18, @empname = 'S';
EXEC dbo.AddEmp @empid = 21, @mgrid =    8, @leftempid =   19, @rightempid =   20, @empname = 'T';
GO

SELECT *
FROM dbo.Employees

-- Data before normalization
SELECT
  empid,
  REPLICATE(' | ', lvl) + empname AS emp,
  hid,
  hid.ToString() AS path
FROM dbo.Employees
ORDER BY hid;

-- Normalize
WITH EmpsRN AS
(
  SELECT
    empid,
    hid,
    ROW_NUMBER() OVER(PARTITION BY hid.GetAncestor(1) ORDER BY hid) AS rownum
  FROM dbo.Employees
),
EmpPaths AS
(
  SELECT empid, hid, CAST('/' AS VARCHAR(900)) AS path
  FROM dbo.Employees
  WHERE hid = hierarchyid::GetRoot()

  UNION ALL

  SELECT C.empid, C.hid,
    CAST(P.path + CAST(C.rownum AS VARCHAR(20)) + '/' AS VARCHAR(900))
  FROM EmpPaths AS P
    JOIN EmpsRN AS C
      ON C.hid.GetAncestor(1) = P.hid
)
UPDATE E
  SET hid = CAST(EP.path AS HIERARCHYID)
FROM dbo.Employees AS E
  JOIN EmpPaths AS EP
    ON E.empid = EP.empid;

-- Data after normalization
SELECT
  empid,
  REPLICATE(' | ', lvl) + empname AS emp,
  hid,
  hid.ToString() AS path
FROM dbo.Employees
ORDER BY hid;

---------------------------------------------------------------------
-- Convert parent-child representation to new hierarchyid
---------------------------------------------------------------------

SET NOCOUNT ON;
USE tempdb;
GO
IF OBJECT_ID('dbo.EmployeesOld') IS NOT NULL
  DROP TABLE dbo.EmployeesOld;
GO
IF OBJECT_ID('dbo.EmployeesNew') IS NOT NULL
  DROP TABLE dbo.EmployeesNew;
GO
CREATE TABLE dbo.EmployeesOld
(
  empid   INT          PRIMARY KEY,
  mgrid   INT          NULL REFERENCES dbo.EmployeesOld,
  empname VARCHAR(25)  NOT NULL,
  salary  MONEY        NOT NULL
);
CREATE UNIQUE INDEX idx_unc_mgrid_empid ON dbo.EmployeesOld(mgrid, empid);

INSERT INTO dbo.EmployeesOld(empid, mgrid, empname, salary) VALUES
  (1,  NULL, 'David',  $10000.00),
  (2,  1,    'Eitan',   $7000.00),
  (3,  1,    'Ina',     $7500.00),
  (4,  2,    'Seraph',  $5000.00),
  (5,  2,    'Jiru',    $5500.00),
  (6,  2,    'Steve',   $4500.00),
  (7,  3,    'Aaron',   $5000.00),
  (8,  5,    'Lilach',  $3500.00),
  (9,  7,    'Rita',    $3000.00),
  (10, 5,    'Sean',    $3000.00),
  (11, 7,    'Gabriel', $3000.00),
  (12, 9,    'Emilia' , $2000.00),
  (13, 9,    'Michael', $2000.00),
  (14, 9,    'Didi',    $1500.00);
GO

CREATE TABLE dbo.EmployeesNew
(
  empid   INT NOT NULL PRIMARY KEY,
  hid     HIERARCHYID NOT NULL,
  lvl AS hid.GetLevel() PERSISTED,
  empname VARCHAR(25) NOT NULL,
  salary  MONEY       NOT NULL
);
GO

WITH EmpsRN
AS
(
  SELECT empid, mgrid, empname, salary,
    ROW_NUMBER() OVER(PARTITION BY mgrid ORDER BY empid) AS rn
  FROM dbo.EmployeesOld
),
EmpPaths AS
(
  SELECT empid, mgrid, empname, salary,
    CAST('/' AS VARCHAR(900)) AS cpath
  FROM dbo.EmployeesOld
  WHERE mgrid IS NULL

  UNION ALL

  SELECT C.empid, C.mgrid, C.empname, C.salary,
    CAST(cpath + CAST(C.rn AS VARCHAR(20)) + '/' AS VARCHAR(900))
  FROM EmpPaths AS P
    JOIN EmpsRN AS C
      ON C.mgrid = P.empid
)
INSERT INTO dbo.EmployeesNew(empid, empname, salary, hid)
  SELECT empid, empname, salary,
    CAST(cpath AS HIERARCHYID) AS hid
  FROM EmpPaths;

SELECT REPLICATE(' | ', lvl) + empname AS empname, hid.ToString() AS path
FROM dbo.EmployeesNew
ORDER BY hid;

---------------------------------------------------------------------
-- Sorting Separated Lists of Values
---------------------------------------------------------------------

USE tempdb;
IF OBJECT_ID('dbo.IPs', 'U') IS NOT NULL DROP TABLE dbo.IPs;

-- Creation script for table IPs
CREATE TABLE dbo.IPs
(
  ip varchar(15) NOT NULL,
  CONSTRAINT PK_IPs PRIMARY KEY(ip),
  -- CHECK constraint that validates IPs
  CONSTRAINT CHK_IP_valid CHECK
  (
      -- 3 periods and no empty octets
      ip LIKE '_%._%._%._%'
    AND
      -- not 4 periods or more
      ip NOT LIKE '%.%.%.%.%'
    AND
      -- no characters other than digits and periods
      ip NOT LIKE '%[^0-9.]%'
    AND
      -- not more than 3 digits per octet
      ip NOT LIKE '%[0-9][0-9][0-9][0-9]%'
    AND
      -- NOT 300 - 999
      ip NOT LIKE '%[3-9][0-9][0-9]%'
    AND
      -- NOT 260 - 299
      ip NOT LIKE '%2[6-9][0-9]%'
    AND
      -- NOT 256 - 259
      ip NOT LIKE '%25[6-9]%'
  )
);
GO

-- Sample data
INSERT INTO dbo.IPs(ip) VALUES
  ('131.107.2.201'),
  ('131.33.2.201'),
  ('131.33.2.202'),
  ('3.107.2.4'),
  ('3.107.3.169'),
  ('3.107.104.172'),
  ('22.107.202.123'),
  ('22.20.2.77'),
  ('22.156.9.91'),
  ('22.156.89.32');

-- IP Patterns
IF OBJECT_ID('dbo.IPPatterns') IS NOT NULL DROP VIEW dbo.IPPatterns;
GO
CREATE VIEW dbo.IPPatterns
AS

SELECT
  REPLICATE('_', N1.n) + '.' + REPLICATE('_', N2.n) + '.'
    + REPLICATE('_', N3.n) + '.' + REPLICATE('_', N4.n) AS pattern,
  N1.n AS l1, N2.n AS l2, N3.n AS l3, N4.n AS l4,
  1 AS s1, N1.n+2 AS s2, N1.n+N2.n+3 AS s3, N1.n+N2.n+N3.n+4 AS s4
FROM dbo.Nums AS N1, dbo.Nums AS N2, dbo.Nums AS N3, dbo.Nums AS N4
WHERE N1.n <= 3 AND N2.n <= 3 AND N3.n <= 3 AND N4.n <= 3;
GO

-- Sort IPs, solution 1
SELECT ip
FROM dbo.IPs
  JOIN dbo.IPPatterns
    ON ip LIKE pattern
ORDER BY
  CAST(SUBSTRING(ip, s1, l1) AS TINYINT),
  CAST(SUBSTRING(ip, s2, l2) AS TINYINT),
  CAST(SUBSTRING(ip, s3, l3) AS TINYINT),
  CAST(SUBSTRING(ip, s4, l4) AS TINYINT);

-- Sort IPs, solution 2
SELECT ip
FROM dbo.IPs
ORDER BY CAST('/' + ip + '/' AS HIERARCHYID);

-- Generic form of problem
SET NOCOUNT ON;
USE tempdb;
IF OBJECT_ID('dbo.T1', 'U') IS NOT NULL DROP TABLE dbo.T1;

CREATE TABLE dbo.T1
(
  id  INT          NOT NULL IDENTITY PRIMARY KEY,
  val VARCHAR(500) NOT NULL
);
GO

INSERT INTO dbo.T1(val) VALUES
  ('100'),
  ('7,4,250'),
  ('22,40,5,60,4,100,300,478,19710212'),
  ('22,40,5,60,4,99,300,478,19710212'),
  ('22,40,5,60,4,99,300,478,9999999'),
  ('10,30,40,50,20,30,40'),
  ('7,4,250'),
  ('-1'),
  ('-2'),
  ('-11'),
  ('-22'),
  ('-123'),
  ('-321'),
  ('22,40,5,60,4,-100,300,478,19710212'),
  ('22,40,5,60,4,-99,300,478,19710212');

SELECT id, val
FROM dbo.T1
ORDER BY CAST('/' + REPLACE(val, ',', '/') + '/' AS HIERARCHYID);

---------------------------------------------------------------------
-- Nested Sets嵌套集合
---------------------------------------------------------------------

---------------------------------------------------------------------
-- Assigning Left and Right Values 分配左值和右值
---------------------------------------------------------------------

-- Producing Binary Sort Paths Representing Nested Sets Relationships
USE tempdb;
GO
-- Create index to speed sorting siblings by empname, empid
CREATE UNIQUE INDEX idx_unc_mgrid_empname_empid
  ON dbo.Employees(mgrid, empname, empid);
GO

DECLARE @root AS INT = 1;

-- CTE with two numbers: 1 and 2
WITH TwoNums
AS
(
  SELECT n FROM(VALUES(1),(2)) AS D(n)
),
-- CTE with two binary sort paths for each node:
--   One smaller than descendants sort paths
--   One greater than descendants sort paths
SortPath
AS
(
  SELECT empid, 0 AS lvl, n,
    CAST(n AS VARBINARY(MAX)) AS sort_path
  FROM dbo.Employees CROSS JOIN TwoNums
  WHERE empid = @root

  UNION ALL

  SELECT C.empid, P.lvl + 1, TN.n,
    P.sort_path + CAST(
      (-1+ROW_NUMBER() OVER(PARTITION BY C.mgrid
                        -- *** determines order of siblings ***
                        ORDER BY C.empname, C.empid))/2*2+TN.n
      AS BINARY(4))
  FROM SortPath AS P
    JOIN dbo.Employees AS C
      ON P.n = 1
      AND C.mgrid = P.empid
    CROSS JOIN TwoNums AS TN
)
SELECT * FROM SortPath
ORDER BY sort_path;
GO

-- CTE Code That Creates Nested Sets Relationships
DECLARE @root AS INT = 1;

-- CTE with two numbers: 1 and 2
WITH TwoNums
AS
(
  SELECT n FROM(VALUES(1),(2)) AS D(n)
),
-- CTE with two binary sort paths for each node:
--   One smaller than descendants sort paths
--   One greater than descendants sort paths
SortPath
AS
(
  SELECT empid, 0 AS lvl, n,
    CAST(n AS VARBINARY(MAX)) AS sort_path
  FROM dbo.Employees CROSS JOIN TwoNums
  WHERE empid = @root

  UNION ALL

  SELECT C.empid, P.lvl + 1, TN.n,
    P.sort_path + CAST(
      ROW_NUMBER() OVER(PARTITION BY C.mgrid
                        -- *** determines order of siblings ***
                        ORDER BY C.empname, C.empid, TN.n)
      AS BINARY(4))
  FROM SortPath AS P
    JOIN dbo.Employees AS C
      ON P.n = 1
      AND C.mgrid = P.empid
    CROSS JOIN TwoNums AS TN
),
-- CTE with Row Numbers Representing sort_path Order
Sort
AS
(
  SELECT empid, lvl,
    ROW_NUMBER() OVER(ORDER BY sort_path) AS sortval
  FROM SortPath
),
-- CTE with Left and Right Values Representing
-- Nested Sets Relationships
NestedSets
AS
(
  SELECT empid, lvl, MIN(sortval) AS lft, MAX(sortval) AS rgt
  FROM Sort
  GROUP BY empid, lvl
)
SELECT * FROM NestedSets
ORDER BY lft;
GO

-- Materializing Nested Sets Relationships in a Table
SET NOCOUNT ON;
USE tempdb;
GO

DECLARE @root AS INT = 1;

WITH TwoNums
AS
(
  SELECT n FROM(VALUES(1),(2)) AS D(n)
),
SortPath
AS
(
  SELECT empid, 0 AS lvl, n,
    CAST(n AS VARBINARY(MAX)) AS sort_path
  FROM dbo.Employees CROSS JOIN TwoNums
  WHERE empid = @root

  UNION ALL

  SELECT C.empid, P.lvl + 1, TN.n,
    P.sort_path + CAST(
      ROW_NUMBER() OVER(PARTITION BY C.mgrid
                        -- *** determines order of siblings ***
                        ORDER BY C.empname, C.empid, TN.n)
      AS BINARY(4))
  FROM SortPath AS P
    JOIN dbo.Employees AS C
      ON P.n = 1
      AND C.mgrid = P.empid
    CROSS JOIN TwoNums AS TN
),
Sort
AS
(
  SELECT empid, lvl,
    ROW_NUMBER() OVER(ORDER BY sort_path) AS sortval
  FROM SortPath
),
NestedSets
AS
(
  SELECT empid, lvl, MIN(sortval) AS lft, MAX(sortval) AS rgt
  FROM Sort
  GROUP BY empid, lvl
)
SELECT E.empid, E.empname, E.salary, NS.lvl, NS.lft, NS.rgt
INTO dbo.EmployeesNS
FROM NestedSets AS NS
  JOIN dbo.Employees AS E
    ON E.empid = NS.empid;

ALTER TABLE dbo.EmployeesNS ADD PRIMARY KEY NONCLUSTERED(empid);
CREATE UNIQUE CLUSTERED INDEX idx_unc_lft_rgt ON dbo.EmployeesNS(lft, rgt);
GO

---------------------------------------------------------------------
-- Querying
---------------------------------------------------------------------

-- Descendants of a given root
SELECT C.empid, REPLICATE(' | ', C.lvl - P.lvl) + C.empname AS empname
FROM dbo.EmployeesNS AS P
  JOIN dbo.EmployeesNS AS C
    ON P.empid = 3
    AND C.lft >= P.lft AND C.rgt <= P.rgt
ORDER BY C.lft;

-- Descendants of a given root, limiting 2 levels
SELECT C.empid, REPLICATE(' | ', C.lvl - P.lvl) + C.empname AS empname
FROM dbo.EmployeesNS AS P
  JOIN dbo.EmployeesNS AS C
    ON P.empid = 3
    AND C.lft >= P.lft AND C.rgt <= P.rgt
    AND C.lvl - P.lvl <= 2
ORDER BY C.lft;

-- Leaf nodes under a given root
SELECT C.empid, C.empname
FROM dbo.EmployeesNS AS P
  JOIN dbo.EmployeesNS AS C
    ON P.empid = 3
    AND C.lft >= P.lft AND C.rgt <= P.rgt
WHERE C.rgt - C.lft = 1;

-- Count of subordinates of each node
SELECT empid, (rgt - lft - 1) / 2 AS cnt,
  REPLICATE(' | ', lvl) + empname AS empname
FROM dbo.EmployeesNS
ORDER BY lft;

-- Ancestors of a given node
SELECT P.empid, P.empname, P.lvl
FROM dbo.EmployeesNS AS P
  JOIN dbo.EmployeesNS AS C
    ON C.empid = 14
    AND C.lft >= P.lft AND C.rgt <= P.rgt;
GO

-- Cleanup
DROP TABLE dbo.EmployeesNS;
GO

---------------------------------------------------------------------
-- Transitive Closure
---------------------------------------------------------------------

---------------------------------------------------------------------
-- Directed Acyclic Graph (DAG)
---------------------------------------------------------------------

-- Transitive Closure of BOM (DAG)
WITH BOMTC
AS
(
  -- Return all first-level containment relationships
  SELECT assemblyid, partid
  FROM dbo.BOM
  WHERE assemblyid IS NOT NULL

  UNION ALL

  -- Return next-level containment relationships
  SELECT P.assemblyid, C.partid
  FROM BOMTC AS P
    JOIN dbo.BOM AS C
      ON C.assemblyid = P.partid
)
-- Return distinct pairs that have
-- transitive containment relationships
SELECT DISTINCT assemblyid, partid
FROM BOMTC;
GO

-- Listing 12-4: Creation Script for the BOMTC UDF
IF OBJECT_ID('dbo.BOMTC') IS NOT NULL
  DROP FUNCTION dbo.BOMTC;
GO

CREATE FUNCTION BOMTC() RETURNS @BOMTC TABLE
(
  assemblyid INT NOT NULL,
  partid     INT NOT NULL,
  PRIMARY KEY (assemblyid, partid)
)
AS
BEGIN
  INSERT INTO @BOMTC(assemblyid, partid)
    SELECT assemblyid, partid
    FROM dbo.BOM
    WHERE assemblyid IS NOT NULL

  WHILE @@rowcount > 0
    INSERT INTO @BOMTC
    SELECT P.assemblyid, C.partid
    FROM @BOMTC AS P
      JOIN dbo.BOM AS C
        ON C.assemblyid = P.partid
    WHERE NOT EXISTS
      (SELECT * FROM @BOMTC AS P2
       WHERE P2.assemblyid = P.assemblyid
       AND P2.partid = C.partid);

  RETURN;
END
GO

-- Use the BOMTC UDF
SELECT assemblyid, partid FROM BOMTC();
GO

-- All Paths in BOM
WITH BOMPaths
AS
(
  SELECT assemblyid, partid,
    1 AS distance, -- distance in first level is 1
    -- path in first level is .assemblyid.partid.
    '.' + CAST(assemblyid AS VARCHAR(MAX)) +
    '.' + CAST(partid     AS VARCHAR(MAX)) + '.' AS path
  FROM dbo.BOM
  WHERE assemblyid IS NOT NULL

  UNION ALL

  SELECT P.assemblyid, C.partid,
    -- distance in next level is parent's distance + 1
    P.distance + 1,
    -- path in next level is parent_path.child_partid.
    P.path + CAST(C.partid AS VARCHAR(MAX)) + '.'
  FROM BOMPaths AS P
    JOIN dbo.BOM AS C
      ON C.assemblyid = P.partid
)
-- Return all paths
SELECT * FROM BOMPaths;

-- Shortest Paths in BOM
WITH BOMPaths -- All paths
AS
(
  SELECT assemblyid, partid,
    1 AS distance,
    '.' + CAST(assemblyid AS VARCHAR(MAX)) +
    '.' + CAST(partid     AS VARCHAR(MAX)) + '.' AS path
  FROM dbo.BOM
  WHERE assemblyid IS NOT NULL

  UNION ALL

  SELECT P.assemblyid, C.partid,
    P.distance + 1,
    P.path + CAST(C.partid AS VARCHAR(MAX)) + '.'
  FROM BOMPaths AS P
    JOIN dbo.BOM AS C
      ON C.assemblyid = P.partid
),
BOMMinDist AS -- Minimum distance for each pair
(
  SELECT assemblyid, partid, MIN(distance) AS mindist
  FROM BOMPaths
  GROUP BY assemblyid, partid
)
-- Shortest path for each pair
SELECT BP.*
FROM BOMMinDist AS BMD
  JOIN BOMPaths AS BP
    ON BMD.assemblyid = BP.assemblyid
    AND BMD.partid = BP.partid
    AND BMD.mindist = BP.distance;
GO

---------------------------------------------------------------------
-- Undirected Cyclic Graph
---------------------------------------------------------------------

-- Transitive Closure of Roads (Undirected Cyclic Graph)
WITH Roads2 -- Two rows for each pair (f-->t, t-->f)
AS
(
  SELECT city1 AS from_city, city2 AS to_city FROM dbo.Roads
  UNION ALL
  SELECT city2, city1 FROM dbo.Roads
),
RoadPaths AS
(
  -- Return all first-level reachability pairs
  SELECT from_city, to_city,
    -- path is needed to identify cycles
    CAST('.' + from_city + '.' + to_city + '.' AS VARCHAR(MAX)) AS path
  FROM Roads2

  UNION ALL

  -- Return next-level reachability pairs
  SELECT F.from_city, T.to_city,
    CAST(F.path + T.to_city + '.' AS VARCHAR(MAX))
  FROM RoadPaths AS F
    JOIN Roads2 AS T
      -- if to_city appears in from_city's path, cycle detected
      ON CASE WHEN F.path LIKE '%.' + T.to_city + '.%'
              THEN 1 ELSE 0 END = 0
      AND F.to_city = T.from_city
)
-- Return Transitive Closure of Roads
SELECT DISTINCT from_city, to_city
FROM RoadPaths;
GO

-- Creation Script for the RoadsTC UDF
IF OBJECT_ID('dbo.RoadsTC') IS NOT NULL
  DROP FUNCTION dbo.RoadsTC;
GO

CREATE FUNCTION dbo.RoadsTC() RETURNS @RoadsTC TABLE (
  from_city VARCHAR(3) NOT NULL,
  to_city   VARCHAR(3) NOT NULL,
  PRIMARY KEY (from_city, to_city)
)
AS
BEGIN
  DECLARE @added as INT;

  INSERT INTO @RoadsTC(from_city, to_city)
    SELECT city1, city2 FROM dbo.Roads;

  SET @added = @@rowcount;

  INSERT INTO @RoadsTC
    SELECT city2, city1 FROM dbo.Roads

  SET @added = @added + @@rowcount;

  WHILE @added > 0 BEGIN

    INSERT INTO @RoadsTC
      SELECT DISTINCT TC.from_city, R.city2
      FROM @RoadsTC AS TC
        JOIN dbo.Roads AS R
          ON R.city1 = TC.to_city
      WHERE NOT EXISTS
        (SELECT * FROM @RoadsTC AS TC2
         WHERE TC2.from_city = TC.from_city
           AND TC2.to_city = R.city2)
        AND TC.from_city <> R.city2;

    SET @added = @@rowcount;

    INSERT INTO @RoadsTC
      SELECT DISTINCT TC.from_city, R.city1
      FROM @RoadsTC AS TC
        JOIN dbo.Roads AS R
          ON R.city2 = TC.to_city
      WHERE NOT EXISTS
        (SELECT * FROM @RoadsTC AS TC2
         WHERE TC2.from_city = TC.from_city
           AND TC2.to_city = R.city1)
        AND TC.from_city <> R.city1;

    SET @added = @added + @@rowcount;
  END
  RETURN;
END
GO

-- Use the RoadsTC UDF
SELECT * FROM dbo.RoadsTC();
GO

-- All paths and distances in Roads (15262 rows)
WITH Roads2
AS
(
  SELECT city1 AS from_city, city2 AS to_city, distance FROM dbo.Roads
  UNION ALL
  SELECT city2, city1, distance FROM dbo.Roads
),
RoadPaths AS
(
  SELECT from_city, to_city, distance,
    CAST('.' + from_city + '.' + to_city + '.' AS VARCHAR(MAX)) AS path
  FROM Roads2

  UNION ALL

  SELECT F.from_city, T.to_city, F.distance + T.distance,
    CAST(F.path + T.to_city + '.' AS VARCHAR(MAX))
  FROM RoadPaths AS F
    JOIN Roads2 AS T
      ON CASE WHEN F.path LIKE '%.' + T.to_city + '.%'
              THEN 1 ELSE 0 END = 0
      AND F.to_city = T.from_city
)
-- Return all paths and distances
SELECT * FROM RoadPaths;

-- Shortest paths in Roads
WITH Roads2
AS
(
  SELECT city1 AS from_city, city2 AS to_city, distance FROM dbo.Roads
  UNION ALL
  SELECT city2, city1, distance FROM dbo.Roads
),
RoadPaths AS
(
  SELECT from_city, to_city, distance,
    CAST('.' + from_city + '.' + to_city + '.' AS VARCHAR(MAX)) AS path
  FROM Roads2

  UNION ALL

  SELECT F.from_city, T.to_city, F.distance + T.distance,
    CAST(F.path + T.to_city + '.' AS VARCHAR(MAX))
  FROM RoadPaths AS F
    JOIN Roads2 AS T
      ON CASE WHEN F.path LIKE '%.' + T.to_city + '.%'
              THEN 1 ELSE 0 END = 0
      AND F.to_city = T.from_city
),
RoadsMinDist -- Min distance for each pair in TC
AS
(
  SELECT from_city, to_city, MIN(distance) AS mindist
  FROM RoadPaths
  GROUP BY from_city, to_city
)
-- Return shortest paths and distances
SELECT RP.*
FROM RoadsMinDist AS RMD
  JOIN RoadPaths AS RP
    ON RMD.from_city = RP.from_city
    AND RMD.to_city = RP.to_city
    AND RMD.mindist = RP.distance;
GO

-- Load Shortest Road Paths Into a Table
WITH Roads2
AS
(
  SELECT city1 AS from_city, city2 AS to_city, distance FROM dbo.Roads
  UNION ALL
  SELECT city2, city1, distance FROM dbo.Roads
),
RoadPaths AS
(
  SELECT from_city, to_city, distance,
    CAST('.' + from_city + '.' + to_city + '.' AS VARCHAR(MAX)) AS path
  FROM Roads2

  UNION ALL

  SELECT F.from_city, T.to_city, F.distance + T.distance,
    CAST(F.path + T.to_city + '.' AS VARCHAR(MAX))
  FROM RoadPaths AS F
    JOIN Roads2 AS T
      ON CASE WHEN F.path LIKE '%.' + T.to_city + '.%'
              THEN 1 ELSE 0 END = 0
      AND F.to_city = T.from_city
),
RoadsMinDist
AS
(
  SELECT from_city, to_city, MIN(distance) AS mindist
  FROM RoadPaths
  GROUP BY from_city, to_city
)
SELECT RP.*
INTO dbo.RoadPaths
FROM RoadsMinDist AS RMD
  JOIN RoadPaths AS RP
    ON RMD.from_city = RP.from_city
    AND RMD.to_city = RP.to_city
    AND RMD.mindist = RP.distance;

CREATE UNIQUE CLUSTERED INDEX idx_uc_from_city_to_city
  ON dbo.RoadPaths(from_city, to_city);
GO

-- Return shortest path between Los Angeles and New York
SELECT * FROM dbo.RoadPaths
WHERE from_city = 'LAX' AND to_city = 'JFK';
GO

-- Creation Script for the RoadsTC UDF
IF OBJECT_ID('dbo.RoadsTC') IS NOT NULL
  DROP FUNCTION dbo.RoadsTC;
GO
CREATE FUNCTION dbo.RoadsTC() RETURNS @RoadsTC TABLE
(
  uniquifier INT          NOT NULL IDENTITY,
  from_city  VARCHAR(3)   NOT NULL,
  to_city    VARCHAR(3)   NOT NULL,
  distance   INT          NOT NULL,
  route      VARCHAR(MAX) NOT NULL,
  PRIMARY KEY (from_city, to_city, uniquifier)
)
AS
BEGIN
  DECLARE @added AS INT;

  INSERT INTO @RoadsTC
    SELECT city1 AS from_city, city2 AS to_city, distance,
      '.' + city1 + '.' + city2 + '.'
    FROM dbo.Roads;

  SET @added = @@rowcount;

  INSERT INTO @RoadsTC
    SELECT city2, city1, distance, '.' + city2 + '.' + city1 + '.'
    FROM dbo.Roads;

  SET @added = @added + @@rowcount;

  WHILE @added > 0 BEGIN
    INSERT INTO @RoadsTC
      SELECT DISTINCT TC.from_city, R.city2,
        TC.distance + R.distance, TC.route + city2 + '.'
      FROM @RoadsTC AS TC
        JOIN dbo.Roads AS R
          ON R.city1 = TC.to_city
      WHERE NOT EXISTS
        (SELECT * FROM @RoadsTC AS TC2
         WHERE TC2.from_city = TC.from_city
           AND TC2.to_city = R.city2
           AND TC2.distance <= TC.distance + R.distance)
        AND TC.from_city <> R.city2;

    SET @added = @@rowcount;

    INSERT INTO @RoadsTC
      SELECT DISTINCT TC.from_city, R.city1,
        TC.distance + R.distance, TC.route + city1 + '.'
      FROM @RoadsTC AS TC
        JOIN dbo.Roads AS R
          ON R.city2 = TC.to_city
      WHERE NOT EXISTS
        (SELECT * FROM @RoadsTC AS TC2
         WHERE TC2.from_city = TC.from_city
           AND TC2.to_city = R.city1
           AND TC2.distance <= TC.distance + R.distance)
        AND TC.from_city <> R.city1;

    SET @added = @added + @@rowcount;
  END
  RETURN;
END
GO

-- Return shortest paths and distances
SELECT from_city, to_city, distance, route
FROM (SELECT from_city, to_city, distance, route,
        RANK() OVER (PARTITION BY from_city, to_city
                     ORDER BY distance) AS rk
      FROM dbo.RoadsTC()) AS RTC
WHERE rk = 1;
GO

-- Cleanup
DROP TABLE dbo.RoadPaths;
GO