mysql - 使用 select sql 将两个表显示为一个表

Question

我有表A

============
| id | val |
=====+======
| 1  | abc |
| 1  | def |
| 2  | ghi |
| 2  | jkl |
============

我有表B

============
| id | val2 |
=====+======
| 1  | rty |
| 1  | vbn |
| 2  | uio |
| 2  | zxc |
============

我想像这样显示两个表格..

===================
| id | val | val2 |
=====+=====+=======
| 1  | abc | rty  |
| 1  | def | vbn  |
| 2  | ghi | uio  |
| 2  | jkl | zxc  |
===================

我的问题是我有冗余..

Answer 1

是的，您遇到问题是因为您没有正确的加入 key 。您可以通过使用变量来创建变量来完成此操作。像这样的东西适用于您提供的数据:

select min(id), max(aval), max(bval)
from ((select id, val as aval, NULL as bval, @rna := @rna + 1 as seqnum
       from tablea a cross join (select @rna := 0)
      ) union all
      (select id, NULL val, @rnb := @rnb + 1 as seqnum
       from tableb b cross join (select @rnb := 0)
      )
     ) ab
group by seqnum;