mysql - mysql联合无法正常工作

Question

您好我正在尝试合并两个表。

我的 id 仅存在于左表中，而我的 id 仅存在于右表中。我想得到一张包含所有 id 的表。我试过：

select * from temp_hours as a
    left outer join temp_orders as o on a.proj_id = o.proj_id
union
select * from temp_hours as a
    right outer join temp_orders as o on a.proj_id = o.proj_id

但我得到错误：

Can't reopen table: 'a'

任何想法我怎么能做到这一点？服务器版本：5.0.51a-24+lenny4 (Debian)

Answer 1

按照建议添加括号或更改缩写...

select * from temp_hours as a
    left outer join temp_orders as ao on a.proj_id = ao.proj_id
union
select * from temp_hours as b
    right outer join temp_orders as bo on b.proj_id = bo.proj_id

Answer 2

只需在您的选择查询周围添加一些括号：

(select * from temp_hours as a
    left outer join temp_orders as o on a.proj_id = o.proj_id)
union
(select * from temp_hours as a
    right outer join temp_orders as o on a.proj_id = o.proj_id)

例如，参见文档中的示例。

Answer 3

每个选择都需要括号

(select * from temp_hours as a
    left outer join temp_orders as o on a.proj_id = o.proj_id)
union
(select * from temp_hours as a
    right outer join temp_orders as o on a.proj_id = o.proj_id)

但是，您得到的错误似乎是临时表限制。