Mysql的七种join查询方法

为了大家使用方便代码单独拿出来
左连接 查a表独有和b表共有部分
select * from a left join b on a.key=b.key;
右连接 查b表独有和a表共有部分
select * from a right join b on a.key=b.key;
内连接 查a、b共有部分
select * from a inner join b on a.key=b.key;
只查a独有的部分
select * from a left join b on a.key=b.key where b.key is null;
只查b独有的部分
select * from a right join b on a.key=b.key where a.key is null;
全连接
select * from a left join b on a.key=b.key union select * from a right join b on a.key=b.key;
查a、b共有的部分
select * from a left join b on a.key=b.key where b.key is null union select * from a right join b on a.key=b.key where a.key is null;
oracle 中的全连接和查a、b共有部分
select * from a full outer join b on a.key=b.key
select * from a full outer join b on a.key=b.key where a.key is null or b.key is null