Question

我真的陷入了UNION ALL联盟，下面是Senario

如果我单独运行此查询，我会得到以下结果

1) Select salary as result from employee 
   where empno = '111628548' and seqno = 4   
   order by seqno Desc

result
------ 
$7000
$3000

2) Select descofemp as result from empdetail
   where empno = '111628548' and seqno = 4 
   order by seqno Desc

result
------
very good employee
good employee

上面的

都会产生字符串，所以列是相同的类型。但当我加入上面两个查询与联盟时，我得到类似

的东西

With s1 as (Select salary from employee 
   where empno = '111628548' and seqno = 4   
   order by seqno Desc),

s2 as (Select descofemp from empdetail
   where empno = '111628548' and seqno = 4 
   order by seqno Desc
)
select * from s1                                                    
Union ALL                                                           
select * from s2  

Result
------
$3000
$7000
very good employee
good employee

你可以在这里看到工资的顺序已经改变了，我尝试了很多东西，但是我无法理解为什么订单在UNION ALL中发生变化，是否有人知道或面对这个问题如果是的话请你分享一些亮点如何解决它。

提前谢谢。

此致莫纳

Answer 1

Union 不保证结果的排序。但是，您可以添加订购信息并使用：

With s1 as (Select salary as col, row_number() over (order by seqno desc) as seqnum
   from employee 
   where empno = '111628548' and seqno = 4   
  ),  
s2 as (Select descofemp as col , row_number() over (order by seqno desc) as seqnum
   from empdetail
   where empno = '111628548' and seqno = 4 
)
select col
from (select * from s1                                                    
      Union ALL                                                           
      select * from s2
     ) t
order by seqnum

Union SQL in DB2 SQL Query更新了第一个表的顺序

1 个答案: