Question

mysql> SELECT
   -> IF(status='EndSP',reportId,'') as 'reportId_EndSP'
   -> FROM T_Name LIMIT 10;
+--------------+
| reportId_EndSP |
+--------------+
|                |
|                |
| 270241         |
|                |
| 270242         |
|                |
|                |
| 270244         |
|                |
|                |
+--------------+
10 rows in set (0.00 sec)

But i need to return only the row where status = 'EndSP'

我不需要执行else子句。

我可以通过写

来实现这一点

SELECT reportId FROM T_Name where status='EndSP';

但我需要使用if或case。

修改/更新

我的实际查询类似于

SELECT
   -> IF(status='EndSP',reportId,'') as 'reportId_EndSP',
   -> IF(status='EndSP',createdTS,'') as 'createdTS_EndSP',
   -> IF(status='BeginSP',reportId,'') as 'reportId_BeginSP',
   -> IF(status='BeginSP',createdTS,'') as 'createdTS_BeginSP'
   -> FROM T_Name HAVING reportId_EndSP!='' AND reportId_BeginSP!='' LIMIT  10;

Answer 1

怎么样：

SELECT * FROM (
   SELECT
      IF(status='EndSP',reportId,'') as reportId_EndSP
      FROM T_Name) a
WHERE reportId_EndSP != '' LIMIT 10;

demo http://sqlfiddle.com/#!2/d1167/8

或单一选择版本

SELECT
   IF(status='EndSP',reportId,'') as reportId_EndSP
   FROM T_Name
HAVING reportId_EndSP != '' LIMIT 10;

demo http://sqlfiddle.com/#!2/d1167/9

Answer 2

您不能仅使用 IF / CASE，因为当IF或{{CASE时，它们不会过滤掉结果集中的值调用1}}，结果集已经确定。

Answer 3

SELECT
 reportId as 'reportId_EndSP'
 FROM T_Name where  IF(status='EndSP',reportId,' ') LIMIT 10;

MySQL IF子句问题

3 个答案: