Question

我有两个数据库。这些是core和push。

这是来自subs数据库的core表：

+----+---------+----+----+-----+
| id | service | ad | op | act |
+----+---------+----+----+-----+
| 1  | CHO     | 96 | x  |  1  |
| 2  | CHO     | 98 | x  |  1  |
| 3  | DANG    | 96 | x  |  1  |
| 4  | HOORAY  | 96 | x  |  1  |
| 5  | CHO     | 98 | x  |  1  |
| 6  | DANG    | 96 | x  |  1  |
+----+---------+----+----+-----+

这是buff数据库中的push表：

+----+---------+-------+
| id | service |  sub  |
+----+---------+-------+
| 1  | DANG    | daily |
| 2  | HOORAY  | daily |
| 3  | DANG    | daily |
+----+---------+-------+

我想计算subs和buff。我对subs：

进行了这个查询

select service, ad, op, count(1) as sub where act=1 group by service,ad,op;

RESULT:
+---------+----+----+-----+
| service | ad | op | sub |
+---------+----+----+-----+
|  CHOO   | 96 | x  |  1  |
|  CHOO   | 98 | x  |  2  |
|  HOORAY | 96 | x  |  1  |
|  DANG   | 96 | x  |  2  |
+---------+----+----+-----+

这是buff的查询：

select service, count(1) as pushed
from buff a where sub = 'daily'
group by service;

RESULT:
+---------+---------+
| service |  pushed |
+---------+---------+
|  HOORAY |    1    |
|  DANG   |    2    |
+---------+---------+

所以，我的问题是如何从两个不同的数据库中加入这些表？这是我期望的结果：

 +---------+----+----+-----+--------+
 | service | ad | op | sub | pushed |
 +---------+----+----+-----+--------+
 |  CHOO   | 96 | x  |  1  |    0   |
 |  CHOO   | 98 | x  |  2  |    0   |
 |  HOORAY | 96 | x  |  1  |    1   |
 |  DANG   | 96 | x  |  2  |    2   |
 +---------+----+----+-----+--------+

Answer 1

一种选择是将两个当前子查询连接在一起。我在下面使用了完整的外部联接，因为我们希望处理服务可能只出现在subs或buff表中的可能性，但不能同时出现两者。

SELECT t1.service,
       t1.ad,
       t1.op,
       t1.sub,
       COALESCE(t2.pushed, 0) AS pushed
FROM
(
    SELECT service, ad, op, COUNT(*) AS sub
    FROM subs
    WHERE act = 1
    GROUP BY service,ad,op
) t1
LEFT JOIN
(
    SELECT service, COUNT(1) AS pushed
    FROM buff a
    WHERE sub = 'daily'
    GROUP BY service
) t2
    ON t1.service = t2.service
UNION
SELECT t2.service,
       COALESCE(t1.ad, -1),
       COALESCE(t1.op, -1),
       COALESCE(t1.sub, -1),
       t2.pushed
FROM
(
    SELECT service, ad, op, COUNT(*) AS sub
    FROM subs
    WHERE act = 1
    GROUP BY service,ad,op
) t1
RIGHT JOIN
(
    SELECT service, COUNT(1) AS pushed
    FROM buff a
    WHERE sub = 'daily'
    GROUP BY service
) t2
    ON t1.service = t2.service

Answer 2

使用数据库名称作为带有点的表名前缀，我不检查下面的句子，它只显示了这个想法：

 SELECT service, ad, op, count(1) AS sub FROM core.subs AS t1
 LEFT JOIN push.buff AS t2 ON t1.service=t2.service WHERE t1.act=1
 AND sub = 'daily' GROUP BY t1.service,t1.ad,t1.op

如何从不同的数据库中计算和连接mySQL上的两个表？

2 个答案: