MySQL学习记录--2

--in 子查询 

select * from student where id in (1, 2); 

--not in 不在其中 
select * from student where id not in (1, 2); 

 

--is null 是空 
select * from student where age is null; 

--is not null 不为空 
select * from student where age is not null; 

 

-- distinct去掉重复数据 
select distinct sex from student; 

 

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1、 union和union all进行并集运算 
--union 并集、不重复 
select id, name from student where name like 'ja%' 
union 
select id, name from student where id = 4; 
--并集、重复 
select * from student where name like 'ja%' 
union all 
select * from student; 
2、 intersect进行交集运算 
--交集（相同部分） 
select * from student where name like 'ja%' 
intersect 
select * from student; 

3、 except进行减集运算 
--减集（除相同部分） 
select * from student where name like 'ja%' 
except 
select * from student where name like 'jas%';