Question

我是MySql的初学者，我希望你能帮助我。我想要DTR User Interface，其中有时间和时间。所以我有一个字段 - id_biometrics,empno,datecreated,time_created,status,device问题是，如果员工忘记进入或超时，我想把时间或时间用于“NULL”这里是我编码的。

SELECT start_log.empno AS "Employee Number", start_log.date_created, start_log.time_created AS "Time In", end_log.time_created AS "Time Out"    
FROM biometrics AS start_log
INNER JOIN biometrics AS end_log ON start_log.empno = end_log.empno
WHERE start_log.status =0
AND end_log.status =1
AND start_log.empno =2
GROUP BY start_log.date_created, start_log.empno

如果他在这一天完成他的时间和超时，那么我在这里输出的是。

Employee Number|date_created |Time_in   | Time_Out
             2 | 2013-07-15  | 11:08:07 | 15:00:00

如果他/她忘记了超时或其中的时间，则显示MySQL返回空结果集（即零行）。（查询花了0.0016秒）

我想要的是

Employee Number | date_created |Time_in   | Time_Out
         3      | 2013-07-15   | 11:50:00 | Null

请帮我解决这个问题。我非常感谢你。

Answer 1

你在找这个吗？

SELECT empno, date_created, 
       MIN(CASE WHEN status = 0 THEN time_created END) time_in,
       MIN(CASE WHEN status = 1 THEN time_created END) time_out
  FROM biometrics
 GROUP BY empno, date_created

示例输出：

+-------+--------------+----------+----------+
| empno | date_created | time_in  | time_out |
+-------+--------------+----------+----------+
|     2 | 2013-07-15   | 11:08:07 | 15:00:00 |
|     3 | 2013-07-15   | 11:50:00 | NULL     |
|     4 | 2013-07-15   | NULL     | 16:00:00 |
+-------+--------------+----------+----------+

这是 SQLFiddle 演示

更新如果您可能有多个输入或输出记录，并且您始终要先获取并最后输出，那么只需使用MAX()聚合time_out

SELECT empno, date_created, 
       MIN(CASE WHEN status = 0 THEN time_created END) time_in,
       MAX(CASE WHEN status = 1 THEN time_created END) time_out
  FROM biometrics
 GROUP BY empno, date_created

这是 SQLFiddle 演示

如何在内连接中放置空集

1 个答案: