带有 COUNT 的 MySQL 查询和来自另一个表的连接列

Question

我有 2 个包含多个字段的表。

表 1:

+--------+---+---------------+                                                  
| month  | id| VERDICT_id    |                                                  
+--------+------+------------+                                                  
| 201307 | 1 |             1 |                                                  
| 201307 | 2 |             4 |                                                  
| 201307 | 3 |             2 |                                                  
| 201307 | 4 |             2 |                                                  
| 201307 | 5 |          NULL |                                                  
| 201307 | 6 |             1 |                                                  
+--------+------+------------+

像这样，对于每个新的“月份”，对于每个唯一的“id”，根据表 2 中的值设置“VERDICT_ID”。

表 2:

+----+----------------------------------+
| id | title                            |
+----+----------------------------------+
|  1 | Passed                           |
|  2 | Failed (Component Fault)         |
|  3 | Failed (User Fault)              |
|  4 | Failed (Hardware Issue)          |
+----+----------------------------------+

我做了一个查询，给出了下面的输出

实际输出:

+--------+------------+----------+
| month  | VERDICT_id | COUNT(*) |
+--------+------------+----------+
| 201307 |          1 |        2 |
| 201307 |          2 |        2 |
| 201307 |          4 |        1 |
+--------+------------+----------+

我想要的是，

+--------+------------+----------+
| month  | VERDICT_id | COUNT(*) |
+--------+------------+----------+
| 201307 |          1 |        2 |
| 201307 |          2 |        2 |
| 201307 |          3 |        0 |
| 201307 |          4 |        1 |
+--------+------------+----------+

这两个输出之间的区别是，如果任何 VERDICT_id 一个月不存在，那么我想将 VERDICT_id 和 COUNT 打印为“0”。

但是对于下面的查询这是不可能的。

select month,VERDICT_id, COUNT(*) FROM Table1 
where (month = 201307) AND (VERDICT_id BETWEEN 1 AND 4) GROUP BY month, VERDICT_id;

问。是否可以进行查询以将不存在的 VERDICT_id 和 COUNT 打印为“0”？

Answer 1

试试这个

SELECT v.*, count(t.verdict_id) as cnt FROM 
(
      SELECT month, id as verdict_id 
      from 
          (SELECT DISTINCT month FROM Table1 where (month = 201307)) M , 
          verdictTable
) v
LEFT OUTER JOIN Table1 t ON v.verdict_id = t.verdict_id and v.month = t.month
GROUP BY v.verdict_id, v.month