Question

我是mysql的新手....它可能看起来转储问题....但我已经尝试了3个小时...这里我想做什么....

SELECT
  MERCHANT_ID,
  IFNULL(COUNT(SUBSCRIBE_ID),0)
FROM SUBSCRIBE_TABLE
WHERE
  MERCHANT_ID IS NULL OR 
  MERCHANT_ID IN(1000000000066,1000000000104,1000000000103,1000000000105)
GROUP BY MERCHANT_ID
ORDER BY
  FIND_IN_SET(MERCHANT_ID,'1000000000066,1000000000104,1000000000103,1000000000105');

AND输出是......

+------------------+---------------------------------+
| MERCHANT_ID      |   IFNULL(COUNT(SUBSCRIBE_ID),0) |
+------------------+---------------------------------+
|    1000000000066 |                               2 |
|    1000000000103 |                               1 |
+------------------+---------------------------------+

但我期待以下方式...

+------------------+---------------------------------+
| MERCHANT_ID      |   IFNULL(COUNT(SUBSCRIBE_ID),0) |
+------------------+---------------------------------+
|    1000000000066 |                               2 |
|    1000000000104 |                               0 |
|    1000000000103 |                               1 |
|    1000000000105 |                               0 |
+------------------+---------------------------------+

我尝试添加MERCHANT_ID IS NULL ...但无法获得默认值的结果...... :(

Answer 1

您只会获得实际位于SUBSCRIBE_TABLE的记录。如果要获取所有id的记录，则必须首先使用这些值“创建临时表”（或使用带UNION的子查询），然后将结果加入其中。

您的查询可能如下所示：

SELECT
  merchant_id,
  COUNT(subscribe_id)
FROM
  (SELECT 1000000000066 AS merchant_id, 1 AS SortKey
   UNION ALL
   SELECT 1000000000104 AS merchant_id, 2 AS SortKey
   UNION ALL
   SELECT 1000000000103 AS merchant_id, 3 AS SortKey
   UNION ALL
   SELECT 1000000000105 AS merchant_id, 4 AS SortKey
  ) AS temp
LEFT JOIN subscribe_table USING (merchant_id)
GROUP BY merchant_id
ORDER BY SortKey ASC

我将您的FIND_IN_SET替换为子查询中的列SortKey。 COUNT只计算非空行，如果没有找到则返回0。你不需要围绕它IFNULL。

如果你有超过4 merchant_id个，你可能想要用临时表做同样的事情。请看这里的例子：
Mysql: Create inline table within select statement?

IFNULL用IN语句用mysql

1 个答案: