SQL复习

1、select

SELECT LastName,FirstName FROM Persons

SELECT * FROM Persons

2、distinct

SELECT DISTINCT Company FROM Orders

3、WHERE

SELECT * FROM Persons WHERE city='beijing'

4、AND&OR运算符

SELECT * FROM Persons WHERE FirstName='tomas' AND LastName='carp'

SELECT * FROM Persons WHERE FirstName='tomas' OR LastName='carp'

5、ORDER BY

默认是升序，可以自己添加ASC 和DESC

SELECT Company,OrderNumber FROM Orders ORDER BY Company,OrderNumber  //首先按照Company升序排列，在Company相同的时候按照OrderNumber关键字升序排列

SELECT Company,OrderNumber FROM Orders ORDER BY Company DESC,OrderNumber ASC  //首先按照Company降序排列，在Company相同的时候按照OrderNumber关键字升序排列

6、insert

插入新的行   INSERT INTO Person VALUES('gate','bill','xuanwumen 10','beijing')

插入指定列中的数据  INSERT INTO Person(LastName,Address) VALUES('wilson','champli stree')

7、update

改变表中的元素值

update Person SET FirstName='xiangli' WHERE LastName='wilson'

修改一行中的多个列

update Person SET City='anhui',Address='chinal addre' WHERE LastName='wilson'

8、delete

删除表中的行

DELETE FROM Person  WHERE LastName='wilson'

删除所有行

DELETE * FROM Person

9、TOP语句

Mysql语句中的TOP

SELECT * FROM Persons LIMIT 5

SQL中的TOP

SELECT TOP 2 * FROM Persons

SELECT TOP 50 PERCENT * FROM Persons //选取前50%

10、通配符

% 替代一个或者多个字符

_替代一个字符

[charlist] 字符列中的任意单一字符

[^charlist]或者[!charlist] 不在字符列中任意单一字符

SELECT * FROM Persons WHERE City LIKE '[ALN]%'   //选取City 以‘A','L','N'开头

11、in

SELECT * FROM Persons WHERE LastNames IN ('Adms','Carter') //选取姓氏是adms,carter的人

12、BETWEEN AND

SELECT * FROM Persons WHERE LastName Between 'Adam' AND 'Carter' //字母表顺序排序，在adam和carter（不包括）之间的人

13、使用别名

对表使用别名

SELECT p.ordernumber,po.LastName From Orders AS p,Products AS po WHERE p.LastName='Adam' AND p.FirstName='herry'

对列使用别名

SELECT LastName AS Fambily, FirstName AS Name FROM Persons  //返回的标的名字就变成了Fambily,Name

14、连接

内连接(只要两个表中有匹配的，就返回该行）

SELECT Persons.LastName,Persons.FirstName,Orders.OrderNo FROM Persons,Orders WHERE Persons.Id_p=Order.Id_p

用内连接也就是SELECT Persons.LastName,Persons.FirstName,Orders.OrderNo FROM Persons INNER JOIN Order ON Persons.Id_p=Order.Id_p

左连接（即使右表没有匹配的项，也要返回左表中的所有内容）

SELECT Persons.LastName,Persons.FirstName,Orders.OrderNo FROM Persons LEFT JOIN Order ON Persons.Id_p=Order.Id_p //将返回左表Person中的所有LastName和FirstName选项

右连接（即使左表没有匹配的项，也要返回右表中的所有内容）

SELECT Persons.LastName,Persons.FirstName,Orders.OrderNo FROM Persons RIGHT JOIN Order ON Persons.Id_p=Order.Id_p //将返回右表Orders中的所有OrderNo选项

全连接（列出左表和右表中的所有行，即使两个表没有匹配的选项，实际即使左连接和右连接的结合）

SELECT Persons.LastName,Persons.FirstName,Orders.OrderNo FROM Persons FULL JOIN Order ON Persons.Id_p=Order.Id_p //将返回左表Person中的所有LastName和FirstName选项,返回右表Orders中的所有OrderNo选项

15、union

union合并（如果有相同的值，只选取一个）

union all 合并（如果有相同的值，都选取）

SELECT E_Name FROM Employees_china

UNION

SELECT E_Name FROM Employees_USA

16、select into

从一个表(或者多个表）中选取数据插入到另外一个表

SELECT LastName,FirstName INTO Person_backup FROM Persons

17、CREATE DATABASE

CREATE DATABASE my_db

18、Create table

数据类型：

整型

integer(size),int(size),smallint(size),tinyint(size)

小数

numeric(size,d)(size最大的位数，d小数点右侧的位数），decimal(size,d)

字符

char(size),varchar(size)

日期

data(yyyymmdd)

CREATE TABLE Persons

(

Id_p int,

LastName char(255),

FirstName char(255)

)

19、sql约束

NOT NULL 不容许为空置

CREATE TABLE Persons

(

Id_p int NOT NULL,

LastName char(255)

)

UNIQUE

mysql中

CREATE TABLE Persons

(

Id_p int NOT NULL,

LastName char(255)，

UNIQUE(Id_p)

)

SQL Server/Oracle

CREATE TABLE Persons

(

Id_p int NOT NULL UNIQUE,

LastName char(255)

)

命名unique约束，并且为多个列添加unique约束

mysql/sql

CREATE TABLE Persons

(

Id_p int NOT NULL,

LastName char(255)，

CONSTRAINT uc_PersonID UNIQUE(Id_p,LastName)

)

为表中的某个属性添加约束

ALTER TABLE Persons ADD UNIQUE(Id_p)

ALTER TABLE Persons ADD CONSTAINT uc_PersonID UNIQUE(Id_p,LastName)

撤销表中的每个约束

mysql

ALTER TABLE Persons DROP INDEX uc_PersonID

sql

ALTER TABLE Persons DROP CONSTRAINT uc_PersonID

主键

mysql

CREATE TABLE Persons

(

Id_p int NOT NULL,

LastName char(255)，

PRIMARY KEY (Id_p)

)

SQL Server/Oracle

CREATE TABLE Persons

(

Id_p int NOT NULL PRIMARY KEY,

LastName char(255)

)

定义多个列的primary key

mysql/sql

CREATE TABLE Persons

(

Id_p int NOT NULL ,

LastName char(255),

CONSTRAINT pk_PersonID PRIMARY KEY(Id_p,LastName)

)

修改表格添加primary key

ALTER TABLE Persons ADD PRIMARY KEY(Id_p)

ALTER TABLE Persons ADD CONSTRAINT pk_PersonId PRIMARY KEY(Id_p,LastName)

撤销primary key

mysql

ALTER TABLE Persons DROP PRIMARY KEY(Id_p)

sql

ALTER TABLE persons DROP CONSTRAINT pk_PersonId

外键

mysql

CREATE TABLE Orders

(

Id_p int NOT NULL ,

LastName char(255),

FPREIGN KEY (Id_p) REFERENCES Persons(Id_p)

)

sql

CREATE TABLE Orders

(

Id_p int  FPREIGN KEY REFERENCES Persons(Id_p),

LastName char(255)

)

定义foreign key

mysql/sql

CREATE TABLE Orders

(

Id_p int  ,

LastName char(255),

CONSTRAINT fk_OrdersNo FOREIGN KEY(Id_p) REFERENCES Persons(Id_p)

)

改变表格添加foreign key

ALTER TABLE Orders ADD FOREIGN KEY (Id_p) REFERENCES Persons(Id_p)

ALTER TABLE Orders ADD CONSTRAINT fk_OrdersNo FOREIGN KEY(Id_p) REFERENCES Persons(Id_p)

撤销foreign key

mysql

ALTER TABLE Orders DROP FOREIGN KEY fk_OrdersNo

sql

ALTER TABLE Orders DROP CONSTRAINT fk_OrdersNo

check约束

mysql

CREATE TABLE Persons

(

Id_p int  ,

LastName char(255),

CHECK (Id_p>0)

)

sql

CREATE TABLE Persons

(

Id_p int CHECK (Id_p>0) ,

LastName char(255),

)

给约束加名字

mysql/sql

CREATE TABLE Persons

(

Id_p int  ,

LastName char(255),

City varchar(255),

CONSTRAINT ck_person CHECK (Id_p>0 AND City='longdon')

)

修改表格添加check

ALTER TABLE Persons Add CHECK (Id_p>0）

ALTER TABLE Persons Add CONSTRAINT ck_person CHECK(Id_p>0)

去掉check

mysql

ALTER TABLE Persons DROP CHECK ck_person

sql

ALTER TABLE Persons DROP CONSTRAINT ck_person

DEFAULT约束

CREATE TABLE Persons

(

Id_p int,

City varchar(255) DEFAULT 'sandes'

)

改变表格添加DEFAULT

mysql

ALTER TABLE Persons ALTER City SET DEFAULT 'sandes'

sql

ALTER TABLE Persons ALTER COLUMN City SET DEFAULT 'sandes'

丢掉DEFAULT

mysql

ALTER TABLE Person ALTER City DROP DEFAULT

sql

ALTER TABLE Person ALTER COLUMN City DROP DEFAULT

20、创建索引

CREATE INDEX PersonIdx ON  Person（LastName)

丢弃索引

MYSQL

ALTER TABLE Person DROP INDEX personIdx

21、drop

如果仅仅丢弃表格中的数据

TRUNCATE TABLE Person

22、alter

增加新列

sql

ALTER TABLE Person ADD Birstday data

改变列的数据类型

sql

ALTER TABLE Person ALTER COLUMN Bristday year

删除birstday

ALTER TABLE Person DROP COLUMN Birstday

23、视图

CREATE VIEW [Category sales list] AS SELECT ProductName,price FROM Poducts

24、is null 和is not null

用IS NULL 和IS NOT NULL 来测试NULL数据

SELECT LastName FROM Person WHERE City IS NULL

25、AVG()

SELECT AVG(Price) AS OrderAverage FROM Orders

结果

OrderAverage

950

26、count()

SELECT COUNT(Custormer) AS countcustormer FROM Orders

SELECT COUNT(DISTINCT Custormer) AS countcustormer FROM Orders

27、first(),last(),max(),min(),sum()

SELECT FIRST(Orderprice) AS FirstPrice FROM Orders

SELECT LAST(Orderprice) AS LastPrice FROM Orders

SELECT MAX(Orderprice) AS MAXPrice FROM Orders

SELECT MIN(Orderprice) AS MinPrice FROM Orders

SELECT SUM(Orderprice) AS SumPrice FROM Orders

28、group by

SELECT Customer,SUM(Orderprice) FROM Orders GROUP BY Customer

结果

Customer	SUM(OrderPrice)
Bush	2000
Carter	1700
Adams	2000

29、having

SELECT Customer,SUM(Orderprice) FROM Orders GROUP BY Customer HAVING SUM(Orderprice)>1200

30、ucase(),lcase()

SELEC UCASE(FirstName) AS Famlily FROM Persons //将所有大写转换成小写

SELEC LCASE(FirstName) AS Famlily FROM Persons  //将所有小写转换成大写

31、MID(列名，开始位置，提取字符的个数)

SELECT MID(City,1,3) AS Smallcity FROM Persons

32、len()返回文本中字段的长度

SELECT LEN(City) AS Lencity FROM Persons

33、round(列名，小数的位数)

SELECT Productname,round(price,0) AS UNIPrice FROM Products

34、now()获取当前日期和时间

SELECT Productname,NOW() AS PerDate FROM Products

35、format()对字段格式化

SELECT Productname,FORMAT(NOW(),'YYYY-MM-DD') AS PerDate FROM Products

mysql中没有select into 创建新表，取而代之的是

create table t1(select * from t)