如何从三个表中获得总和? [英] How to get the Sum from three tables?

问题描述

可能的重复:
如何从两个表中获取总和?

我有三个表，第一个products"第二个items"第三个sales"
第一个和第二个表具有相同的列 ('code','quantity') 但第三个表具有 ('code','name') 现在我想要第一个和第二个的总和数量，但还想从第三个表中获取代码相同的名称.检查我的代码

I have three table first "products" second "items" third "sales"
The first and second tables have the same columns('code','quantity') but the third table has ('code','name') now I want sum quantity from first and second but want also want get name from third table which code is equal. check my code

Select code, sum(qtd),name
from (           select a.code, a.qtd from product a
       union all select b.code, b.qtd from items   b
       union all select c.name        from sales   c where b.code=c.code
     )
group by code

前两个给了我完美的值，但第三个小说给出了错误，没有显示名字.

first two giving me perfect values but third fiction giving error not showing also names.

推荐答案

我觉得你想做这样的事情，虽然不清楚实际需求是什么:

I think you want to do something like this, though it's not clear what the actual requirements are:

select code = t1.code ,
       name = t2.name ,
       qtd  = t1.qtd 
from ( select code =      t.code   ,
              qtd  = sum( t.qtd  )
       from (           select a.code, a.qtd from product a
              union all select b.code, b.qtd from items   b
            ) t
       group by t.code
     ) t1
join sales t2 where t2.code = t1.code

干杯！

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