mysql学习04-七种join语句

1.常用的三种

内连接：select select_list from A inner join B on A.key=B.key

左外连接: select select_list from A left join B on A.key=B.key

右外连接: select select_list from A right join B on A.key=B.key

2.用法升级

左连接：select select_list from A left join B on A.key=B.key where B.key is null

右连接：select select_list from A right join B on A.key=B.key where A.key is null

全连接：

select select_list from A left join B on A.key=B.key

union

select select_list from A right join B on A.key=B.key

全外连接：

select select_list from A left join B on A.key=B.key where B.key is null

union

select select_list from A right join B on A.key=B.key where A.key is null