T-SQL 片段收藏

存储过程

 CREATE PROCEDURE spInsertOrUpdateProduct
 --有则更新，否则插入
     @ProductName NVARCHAR(50) ,
     @ProductNumber NVARCHAR(25) ,
     @StdCost MONEY
 AS
     IF EXISTS ( SELECT  *
                 FROM    Production.Product
                 WHERE   ProductNumber = @ProductNumber )
         UPDATE  Production.Product
         SET     Name = @ProductName ,
                 StandardCost = @StdCost
         WHERE   ProductNumber = @ProductNumber
     ELSE
         INSERT  INTO Production.Product
                 ( Name ,
                   ProductNumber ,
                   StandardCost
                 )
                 SELECT  @ProductName ,
                         @ProductNumber ,
                         @StdCost
 
 GO

触发器

 CREATE TRIGGER tr_DelProduct ON Production.Product
     FOR DELETE
 AS
     IF ( SELECT COUNT(*)
          FROM   sales.SalesOrderDetail
                 INNER JOIN DELETED ON salesorderdetail.ProductID = DELETED.productid
        ) > 0
         BEGIN
             RAISERROR ('Cannot delete a product with sales orders',14,1)
             ROLLBACK TRANSACTION
             RETURN
         END

自定义函数

 CREATE FUNCTION dbo.fn_LastOfMonth ( @TheDate DATETIME )
 RETURNS DATETIME
 AS
     BEGIN
         DECLARE @FirstOfMonth DATETIME
         DECLARE @DaysInMonth INT
         DECLARE @RetDate DATETIME
         SET @FirstOfMonth = DATEADD(mm, DATEDIFF(mm, 0, @TheDate), 0)
         SET @DaysInMonth = DATEDIFF(d, @FirstOfMonth,
                                     DATEADD(m, 1, @FirstOfMonth))
         RETURN DATEADD(d,@DaysInMonth-1,@FirstOfMonth)
     END

查看表的元数据，也就是数据的数据

 SELECT  *
 FROM    sys.columns
 WHERE   [object_id] = OBJECT_ID('Production.Product')

不建议用上面的系统试图
可以用数据库视图

 IF NOT EXISTS ( SELECT  *
                 FROM    INFORMATION_SCHEMA.TABLES
                 WHERE   TABLE_NAME = 'Address'
                         AND TABLE_NAME = 'Person' )
     DROP TABLE PERSON.Address
 GO

修改对象

 ALTER PROCEDURE spInsertOrUpdateProduct
     @ProductName NVARCHAR(50) ,
     @ProductNumber NVARCHAR(25) ,
     @StdCost MONEY ,
     @ListPrice MONEY
 AS
     BEGIN TRY
         BEGIN TRANSACTION
         IF EXISTS ( SELECT  *
                     FROM    Production.Product
                     WHERE   ProductNumber = @ProductName )
             UPDATE  Production.Product
             SET     Name = @ProductName ,
                     StandardCost = @StdCost
             WHERE   ProductNumber = @ProductNumber
         ELSE
             INSERT  INTO production.Product
                     ( Name ,
                       ProductNumber ,
                       StandardCost ,
                       ListPrice
                     )
                     SELECT  @ProductName ,
                             @ProductNumber ,
                             @StdCost ,
                             @ListPrice
         COMMIT TRANSACTION
     END TRY
     BEGIN CATCH
         DECLARE @ErrMsg VARCHAR(1000)
         SET @ErrMsg = ERROR_MESSAGE()
         ROLLBACK TRANSACTION
         RAISERROR(@ErrMsg,14,1)
         RETURN
     END CATCH

添加和删除表列

 ALTER TABLE Production.Product
 ADD LeadTime SMALLINT NULL
 
 ALTER TABLE production.Product
 DROP COLUMN LeadTime

WITH TIES用法，找出最贵的一个商品，但最贵的有好多个

 SELECT TOP(1) WITH TIES * FROM Production.Product
 ORDER BY ListPrice DESC
 --返回5条记录

交叉表查询

 CREATE TABLE [Test]
     (
       [id] [int] IDENTITY(1, 1)
                  NOT NULL ,
       [name] [nvarchar](50) COLLATE Chinese_PRC_CI_AS
                             NULL ,
       [subject] [nvarchar](50) COLLATE Chinese_PRC_CI_AS
                                NULL ,
       [Source] [numeric](18, 0) NULL
     )
 ON  [PRIMARY]
 GO
 INSERT  INTO [test]
         ( [name], [subject], [Source] )
 VALUES  ( N'张三', N'语文', 60 ) ,
         ( N'李四', N'数学', 70 ),
         ( N'王五', N'英语', 80 ),
         ( N'王五', N'数学', 75 ),
         ( N'王五', N'语文', 57 ),
         ( N'李四', N'语文', 80 ),
         ( N'张三', N'英语', 100 );
 Go 
 
 SELECT  *
 FROM    test
 
 -------方法一----------
 SELECT  name ,
         SUM(CASE subject
               WHEN '数学' THEN source
               ELSE 0
             END) AS '数学' ,
         SUM(CASE subject
               WHEN '英语' THEN source
               ELSE 0
             END) AS '英语' ,
         SUM(CASE subject
               WHEN '语文' THEN source
               ELSE 0
             END) AS '语文'
 FROM    test
 GROUP BY name
 ------方法二--------
 DECLARE @sql VARCHAR(8000)
 SET @sql = 'select name,'
 SELECT  @sql = @sql + 'sum(case subject when ''' + subject + '''
 then source else 0 end) as ''' + subject + ''','
 FROM    ( SELECT DISTINCT
                     subject
           FROM      test
         ) AS a
 SELECT  @sql = LEFT(@sql, LEN(@sql) - 1) + ' from test group by name'
 EXEC(@sql)
 go

游标

 USE Northwind
 GO
 
 DECLARE curProduct CURSOR
 FOR
     SELECT  ProductID ,
             ProductName
     FROM    dbo.Products
 
 DECLARE @ProdID INT
 DECLARE @ProdName NVARCHAR(100)
 
 OPEN curProduct
 FETCH NEXT FROM curProduct INTO @ProdID, @ProdName
 WHILE @@FETCH_STATUS = 0
     BEGIN
         PRINT @ProdName
         FETCH NEXT FROM curProduct INTO @ProdID, @ProdName
     END
 
 CLOSE curProduct
 DEALLOCATE curProduct
 ---------------------------------------------

CASE用法1

 USE AdventureWorks2008
 GO
 SELECT  ProductID ,
         Name ,
         ListPrice ,
         ProductSubcategoryID ,
         CASE ProductSubcategoryID
           WHEN 1 THEN 'Mountain Bike'
           WHEN 2 THEN 'Road Bike'
           WHEN 3 THEN 'Touring Bike'
           WHEN NULL THEN 'Something Else'
           ELSE '(No SubCategory)'
         END AS SubCategory
 FROM    Production.Product
 ----------------------------------------

CASE用法2

SELECT  ProductID ,
        Name ,
        ListPrice ,
        ProductSubcategoryID ,
        SubCategory = CASE ProductSubcategoryID
                        WHEN 1 THEN 'Mountain Bike'
                        WHEN 2 THEN 'Road Bike'
                        WHEN 3 THEN 'Touring Bike'
                        WHEN NULL THEN 'Something Else'
                        ELSE '(No Subcategory)'
                      END
FROM    Production.Product
-----------------------------------------------------

自动增长列操作1

SET IDENTITY_INSERT myTable ON --关闭自动增长
INSERT myTable(myID, myDescription)
VALUES(5,'This will work')
SET IDENTITY_INSERT myTable OFF --开启自动增长
--------------------------------------------------------------------

表连接

http://blog.163.com/ji_1006/blog/static/10612341201310221261829/