Question

假设我有两个表GOOD和BAD来存储小部件生成的记录。我的表看起来像这样

Widget      Good
----------------
Widget A    Y
Widget A    Y
Widget B    Y

Widget      Bad
----------------
Widget A    Y
Widget B    Y

我有这两个基本查询

select count(*) as good from table_good where widget = 'Widget A' and Good = 'Y'
select count(*) as bad from table_bad where widget = 'Widget A' and Bad = 'Y'

这会产生两个这样的表

good
----
2

bad
---
1

我想将这些组合成一个单独的查询，在那里我会找回一个包含单个记录的表

good    bad
-----------
2       1

有人能指出我该怎么做。我认为做一个联合并在其他表中设置假列会选择这样做，但我得到了正确的表模式，但有两个单独的记录。

谢谢！

Answer 1

试试这个：

SELECT (SELECT COUNT(*) AS good 
        FROM   table_good 
        WHERE  widget = 'Widget A' 
               AND good = 'Y') AS good, 
       (SELECT COUNT(*) AS bad 
        FROM   table_bad 
        WHERE  widget = 'Widget A' 
               AND bad = 'Y')  AS bad 
FROM   dual

Answer 2

另一种方法是使用FULL JOIN：

SELECT COALESCE(A.widget,B.widget) AS Widget, COUNT(G.*) AS Good, COUNT(B.*) AS Bad
FROM table_good G
FULL OUTER JOIN table_bad B
ON G.widget = B.widget AND A.Good = B.Bad
WHERE (G.widget = 'Widget A' OR B.Widget = 'Widget A') 
AND (G.Good = 'Y' OR B.Good = 'Y')

Oracle / SQL - 将来自“不相关”的不相关表的计数组合在一起

2 个答案: