SQL笔记02

use stuinfo
select * from sc
select sno,sname from stu

--,,,as 属性名
select sname,2021-age as birth_date from stu
select sno from sc

--distinct去重
select distinct sno from sc

--查找某姓名学生信息
select * from stu where sname='小十'
select * from stu where sname like '小十'

select sno from sc where cno='20201' and grade>80

select sname,age from stu where age>=18 and age<=19
select sname,age from stu where age between 18 and 19

--in多个or
select * from stu where mno != 3
select * from stu where mno=1 or mno=2 or mno=4
select * from stu where mno in(1,2,4)
select * from stu where mno not in(1,2,4)
--%通配符，模糊查询
select * from stu where sname like '彭%'
--_占位
select * from stu where sname like '_小%'
select * from stu where sname like '%小%'
select * from sc where grade is null