Php &引用;“双重结果”;当我使用case when语句时
表msabsensiPhp &引用;“双重结果”;当我使用case when语句时,php,mysql,phpmyadmin,Php,Mysql,Phpmyadmin,表msabsensi +--------+-----------+-------+----------+----------+------------+------------+ | id | nik | nik_b | in_hr | out_hr | in_date | out_date | +--------+-----------+-------+----------+----------+------------+------------+ |
+--------+-----------+-------+----------+----------+------------+------------+
| id | nik | nik_b | in_hr | out_hr | in_date | out_date |
+--------+-----------+-------+----------+----------+------------+------------+
| 262230 | 216065459 | 5459 | 07:42:00 | 16:37:00 | 2017/10/25 | 2017/10/25 |
| 263430 | 216065459 | 5459 | 07:40:00 | 16:29:00 | 2017/10/26 | 2017/10/26 |
| 264610 | 216065459 | 5459 | 07:38:00 | 20:01:00 | 2017/10/27 | 2017/10/27 |
| 267550 | 216065459 | 5459 | 19:40:00 | 08:38:00 | 2017/10/29 | 2017/10/30 |
| 268870 | 216065459 | 5459 | 23:50:00 | 09:06:00 | 2017/10/30 | 2017/10/31 |
| 270067 | 216065459 | 5459 | 00:00:00 | 08:32:00 | NULL | 2017/11/01 |
| 271359 | 216065459 | 5459 | 23:50:00 | 08:12:00 | 2017/11/01 | 2017/11/02 |
| 272614 | 216065459 | 5459 | 23:48:00 | 08:47:00 | 2017/11/02 | 2017/11/03 |
| 274119 | 216065459 | 5459 | 00:00:00 | 20:10:00 | NULL | 2017/11/04 |
| 274975 | 216065459 | 5459 | 07:46:00 | 00:00:00 | 2017/11/05 | NULL |
+--------+-----------+-------+----------+----------+------------+------------+
表mstanggal
+-----+------------+
| id | tanggal |
+-----+------------+
| 298 | 2017/10/25 |
| 299 | 2017/10/26 |
| 300 | 2017/10/27 |
| 301 | 2017/10/28 |
| 302 | 2017/10/29 |
| 303 | 2017/10/30 |
| 304 | 2017/10/31 |
| 305 | 2017/11/01 |
| 306 | 2017/11/02 |
| 307 | 2017/11/03 |
| 308 | 2017/11/04 |
| 309 | 2017/11/05 |
+-----+------------+
当in_date为空,然后使用out_date时,我在数据库中查询查看考勤(msabsensi)数据
SELECT c.tanggal, b.in_date, b.out_date, b.in_hr, b.out_hr, b.nik from mstanggal c
left outer join msabsensi b on c.tanggal = (CASE WHEN c.tanggal = b.in_date THEN b.in_date ELSE b.out_date END)
where c.tanggal = '2017-11-01' and b.nik = '216065459'
但结果是双重的
+-----------+------------+-----------+----------+----------+-----------+
| tanggal | in_date | out_date | in_hr | out_hr | nik |
+-----------+------------+-----------+----------+----------+-----------+
| 11/1/2017 | 10/31/2017 | 11/1/2017 | 23:46:00 | 08:32:00 | 216065459 |
| 11/1/2017 | 11/1/2017 | 11/2/2017 | 23:50:00 | 08:12:00 | 216065459 |
+-----------+------------+-----------+----------+----------+-----------+
正确的结果是第二条记录
如何只显示那个
+-----------+-----------+-----------+----------+----------+-----------+
| 11/1/2017 | 11/1/2017 | 11/2/2017 | 23:50:00 | 08:12:00 | 216065459 |
+-----------+-----------+-----------+----------+----------+-----------+
你为什么要用case?如果c.tanggal b.in\u date,是否只想获取c.tanggal=b.out\u date的记录?或者您只想查看c.tanggal b.in_日期所在的记录 案例是获取c.tanggal=b.in_日期或c.tanggal=b.out_日期的任何记录。对于第一条记录,第二种情况为真,对于第二条记录,第一种情况为真 如果您只需要在第一个案例没有结果的情况下处理第二个案例,我建议添加另一个加入:
SELECT c.tanggal, ifnull(b.in_date, d.in_date), ifnull(b.out_date, d.out_date), ifnull(b.in_hr,d.in_hr), ifnull(b.out_hr, d.out_hr), ifnull(b.nik,d.nik)
from mstanggal c
left outer join msabsensi b on c.tanggal = b.in_date and b.nik = '216065459'
left outer join msabsensi d on c.tanggal = d.out_date and d.nik = '216065459'
where c.tanggal = '2017-11-01'
使用COALESCE()或IFNULL()
case expression
表达式的计算结果为一个值,(语句不同)没有问题。但是,请注意,这不是“良好做法”,如果表很大,这将对性能造成不良影响,确保输入日期永远不为空更有意义是的,我知道。但在我的位置上,社会化已经完成,总是充满了存在,但人们可以忘记呵呵
SELECT c.tanggal
, b.in_date
, b.out_date
, b.in_hr
, b.out_hr
, b.nik
FROM mstanggal c
LEFT JOIN msabsensi b ON c.tanggal = coalesce(b.in_date, b.out_date)
WHERE c.tanggal = '2017-11-01' AND b.nik = '216065459'