具有不同列数的联盟

Question

我在第一个表中有三列，第二个表中有一列存在于第一个表中，我想添加2个列。

例：

select c1 as col1, c2 as col2, c3 as col3 
from Table1 
union 
select c1, c4 as col4, c5 as col5 
from Table2 

expected Result: 

col1,col2,col3,col4,col5 

Answer 1

只需添加null或任何其他默认值你喜欢静态列

select c1 as col1, 
     c2 as col2, 
     c3 as col3, 
     null as col4, 
     null as col5 
from Table1 
union 
select c1, 
     null, 
     null, 
     c4, 
     c5 
from Table2 

Answer 2

你已经问这个问题，并得到了答案 - https://stackoverflow.com/questions/18923218/unioning-tables-with-different-number-of-columns/18923250#18923250。是还有的，其实你需要一个join，没有工会的可能性：

select 
    t1.c1 as col1, 
    t1.c2 as col2, 
    t1.c3 as col3, 
    t2.c4 as col4, 
    t2.c5 as col5 
from Table1 as t1 
    inner join Table2 as t2 on t2.col1 = t1.col1