联盟从2选择加入

Question

请大家，我需要有关select语法的帮助。

我需要从join中选择两个select结果。

我试着解释

SELECT FROM 2 TABLE BY JOIN 
UNION
SELECT FROM 2 OTHER TABLE BY UNION

OR

我试过了：

select .... join.... data from table2for union
union
select .... join ... data from table1 for union

我将联合的表是2表的连接结果。

了解其他数据：

tabA1
codice
nome
totale
JOIN
tabA2
restocodice
restonome

UNION

tabB1
codiceconf
nomeconf
totaleconf
JOIN
tabB2
restocodiceconf
restonomeconf

我希望我解释过。

Answer 1

select * 
from taba1 
left join taba2 
on taba1.col=taba2.col

union

select * 
from tabb1 
left join tabb2
 on tabb1.col=tabb2.col

Answer 2

这是一般结构：

SELECT cols
FROM table1
JOIN table2 ON join-conditions
WHERE more-conditions

UNION

SELECT cols
FROM table3
JOIN table4 ON join-conditions
WHERE more-conditions