id | name | id | name |
1 | zhangsan | 1 | hanmeimei |
2 | lisi | 2 | wangwu |
3 | wangwu |
join:select * from A join B on A.name=B.name -----取交集
id | name | id | name |
1 | wangwu | 2 | wangwu |
full/out join:select * from A full join B on A.name=B.name ----取并集
id | name | id | name |
1 | zhangsan | null | null |
2 | lisi | null | null |
3 | wangwu | 2 | wangwu |
null | null | 1 | hanmeimei |
left join:select * from A left join B on A.name=B.name
id | name | id | name |
1 | zhangsan | null | null |
2 | lisi | null | null |
3 | wangwu | 2 | wangwu |
right join: select * from A right join B on B.name
id | name | id | name |
null | null | 1 | hanmeimei |
3 | wangwu | 2 | wangwu |
union:select name from A union select name from B(union和union all中的select语句需要相同的查询列)
name |
zhangsan |
lisi |
wangwu |
hanmeimei |
union all:较union区别是union会将重复值合并,而union all不会合并
select name from A union all select name from B
name | ||||
|
||||
wangwu |
转载于:https://www.cnblogs.com/enhance/p/10980459.html