这种简单的MySQL连接对我不起作用

Question

每个单独的查询（t1和t2）本身都能正常工作，但是似乎不允许进行简单的联接。

我使用表x1和x2重新创建了代码，这很好，但是在顶部复制粘贴t1和t2会使我再次出错。

这一定与变量有关吗？

问题尝试：

select *
from
( 
set @rownumber1 = 0;
select  (@rownumber1:= @rownumber1 + 1) as num,
    id,
    updated_at as date,
    risk_factor
from (select * from user.users_audit order by id) orig
order by id 
) t1

left join
(
set @rownumber2 = 0;
select  (@rownumber2:= @rownumber2 + 1) as num,
    id,
    updated_at as date,
    risk_factor
from (select * from user.users_audit order by id) orig
order by id 
) t2 on t1.id = t2.id

尝试工作-但是我不在乎表格：

select *
from
(
select *
from sport_type_sources
) x1

inner join
(
select *
from sport_type_sources
) x2 on x1.id = x2.id

我只是想将两个表合并在一起。