SQL基础

【DISTINCT】

返回唯一不同的值

SELECT DISTINCT 列名称 FROM 表名称

SELECT DISTINCT Company FROM Orders

【WHERE】

=   等于

<> 不等于

>= 大于等于

<= 小于等于

BETWEEN 在某个范围内

LIKE 搜索某种模式

注：

SELECT * FROM Persons WHERE FirstName='Bush'

SELECT * FROM Persons WHERE Year>1965

【AND OR】

SELECT * FROM Persons WHERE FirstName='Thomas' AND LastName='Carter'
SELECT * FROM Persons WHERE firstname='Thomas' OR lastname='Carter'

组合查询
SELECT * FROM Persons WHERE (FirstName='Thomas' OR FirstName='William') AND LastName='Carter'

【ORDER BY】

string 字符序

SELECT Company, OrderNumber FROM Orders ORDER BY Company

SELECT Company, OrderNumber FROM Orders ORDER BY Company, OrderNumber

默认是 ASC，降序用DESC

SELECT Company, OrderNumber FROM Orders ORDER BY Company DESC

有升有降

SELECT Company, OrderNumber FROM Orders ORDER BY Company DESC, OrderNumber ASC

【INSERT】

INSERT INTO Persons (LastName, Address) VALUES ('Wilson', 'Champs-Elysees')

【UPDATE】

UPDATE Person SET FirstName = 'Fred' WHERE LastName = 'Wilson' 

UPDATE Person SET Address = 'Zhongshan 23', City = 'Nanjing'
WHERE LastName = 'Wilson'

【DELETE】

DELETE FROM Person WHERE LastName = 'Wilson' 

DELETE * FROM table_name