单表查询

select sname,2021-age as birthdate from stu

select sno from sc

select distinct sno from sc
查询名字叫小十
select * from stu where sname = ‘小十’

select sno from sc where cno = ‘20201’ and grade >80
查询年龄18-19岁的
select sname from stu where age between 18 and 19
查询专业号是，124的
select * from stu where mno in(1,2,4)
查询专业号不是124的
select * from stu where mno not in(1,2,4)
查询叫彭某的
select * from stu where sname like ‘彭%’
查询名字第二个字是小的
select * from stu where sname like ‘_小%’
查询名字带小的
select * from stu where sname like ‘%小%’

select * from sc
查询成绩为空的
select * from sc where grade is null