全表连接。双表无连接条件。条件为 a.ID = 88 or b.ID = 88
补充内容 (2023-3-30 10:23):
(select ID , key , value , "" as user_id from a where ID = 88) union all (select ID , "" as key , "" as value , user_id from b where ID = 88)
补充内容 (2023-3-30 10:24):
mysql 没有full join的语法。必须要union方法来合并。。
补充内容 (2023-3-30 10:23):
(select ID , key , value , "" as user_id from a where ID = 88) union all (select ID , "" as key , "" as value , user_id from b where ID = 88)
补充内容 (2023-3-30 10:24):
mysql 没有full join的语法。必须要union方法来合并。。