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