SQL 基本语法记录
SQL的基本语法1：select sno,sname from student where sage between 20 and 30 ----查询出20到30之间年纪的人员
2：select sno,sname from student where sage is null -----从student表中查询出年纪为空的人员
3：select sno,sname from student where sname="cary" or sname="mina" or sname "amy"----查询出cary,mina,amy的学号和 名字
还可以使用 select sno,sname from student where sname in('cary','mina','amy') 可以实现同样的功能
select 部分
1：AS 可以为字段重命名
2：distinct 去重复值
3：聚合函数()avg(),max(),min(),sum(),count()
4：TOP5前5行数据select top 5 sno,sname from student
5：Into select top 5 into testtable from student把查询的TOP 5数据存到testtable表中，该testtable表存在于
master数据库的表中
select sno,sname,sage,sex into test table02 from student where 11------获取student表结构
From 部分
1：表重命名
select bookname from book as t1,borrowbook as t2 where t1.id=t2.id----为book表重命名T1 borrowbook 为t2
2：结合子查询
select distinct bookname from book as t1 ,(select distinct bookid from borrowbook) as t2 where t1.bookid=t2.bookid
where 部分
1：数字 ：=，>,,=，
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