联合访问查询

Question

我有关于访问的工会问题。

我有表MyCount

S | A | M | Q
=============
1 |10 |111| 4
1 |10 |222| 5
1 |10 |333| 9
1 |20 |444|10

我有表目录

S | A | M | 
=============
1 |10 |111| 
1 |10 |222| 
1 |10 |333| 
1 |10 |444|
1 |10 |555|
1 |20 |999|
1 |20 |888|
1 |20 |777|

我需要MyCount中的所有数据和目录 - 但是如果数据在MyCount上

不在目录中，它将带有Qty = 0

我需要联合查询，即resault将如下所示：

S | A | M | Q
=============
1 |10 |111| 4 
1 |10 |222| 5 
1 |10 |333| 9 
1 |10 |444| 0
1 |10 |555| 0
1 |20 |999|10
1 |20 |888| 0
1 |20 |777| 0

Answer 1

您可以使用union all：

select s, a, m, q
from mycount
union all
select s, a, m, 0
from catalog as c
where not exists (select 1
                  from mycount as mc
                  where mc.s = c.s and mc.a = c.a and mc.m = c.m
                 );