我有两个mysql select语句，我想从另一个中减去一个：
首先选择声明：
SELECT rec.time_stamp,
rec.day_chan1,
rec.day_chan2,
rec.day_chan3,
rec.total_phase
FROM
(SELECT ".$this->table_name.".*,
DATE(time_stamp) AS mydate,
TIME(time_stamp) AS mytime
FROM ".$this->table_name."
WHERE TIME(time_stamp) >= '00:00:00'
AND TIME(time_stamp) <= '07:59:59') AS rec
JOIN
(SELECT DATE(time_stamp) AS mydate,
MAX(TIME(time_stamp)) AS mytime
FROM ".$this->table_name."
WHERE TIME(time_stamp) >= '00:00:00'
AND TIME(time_stamp) <= '07:59:59'
GROUP BY DATE(time_stamp)) AS max_times ON max_times.mydate = rec.mydate
AND max_times.mytime = rec.mytime
ORDER BY rec.mydate
结果：
+---------------------+-----------+-----------+-----------+-------------+
| time_stamp | day_chan1 | day_chan2 | day_chan3 | total_phase |
+---------------------+-----------+-----------+-----------+-------------+
| 2014-06-03 07:59:48 | 24210 | 22744 | 26003 | 72957 |
| 2014-06-04 07:59:49 | 112603 | 103417 | 121368 | 337388 |
| 2014-06-05 07:59:50 | 21302 | 20165 | 23317 | 64784 |
| 2014-06-06 07:59:50 | 21561 | 20951 | 23875 | 66387 |
| 2014-06-07 07:59:03 | 408 | 1151 | 767 | 2326 |
| 2014-06-08 07:59:04 | 384 | 1151 | 767 | 2302 |
| 2014-06-09 07:59:53 | 21580 | 20656 | 23788 | 66024 |
| 2014-06-10 07:59:54 | 19689 | 18861 | 21657 | 60207 |
| 2014-06-11 07:59:54 | 22283 | 21132 | 24820 | 68235 |
| 2014-06-12 07:59:56 | 20489 | 19327 | 22377 | 62193 |
| 2014-06-13 07:59:56 | 20646 | 19485 | 22504 | 62635 |
| 2014-06-15 07:59:09 | 387 | 1151 | 767 | 2305 |
| 2014-06-16 07:59:58 | 30681 | 29050 | 33593 | 93324 |
| 2014-06-17 07:59:59 | 18248 | 17701 | 20432 | 56381 |
| 2014-06-18 07:37:49 | 40170 | 38123 | 47013 | 125306 |
| 2014-06-19 07:59:38 | 22417 | 21001 | 24484 | 67902 |
| 2014-06-20 07:59:50 | 19104 | 18238 | 21007 | 58349 |
| 2014-06-21 07:59:15 | 384 | 1151 | 767 | 2302 |
| 2014-06-22 07:59:16 | 384 | 1151 | 767 | 2302 |
| 2014-06-23 07:59:53 | 19675 | 18582 | 21114 | 59371 |
| 2014-06-24 07:59:42 | 18341 | 17504 | 19427 | 55272 |
| 2014-06-25 07:59:55 | 19554 | 18469 | 20879 | 58902 |
| 2014-06-26 07:59:55 | 20241 | 19262 | 21881 | 61384 |
| 2014-06-27 07:59:56 | 17984 | 17033 | 19528 | 54545 |
| 2014-06-28 07:59:21 | 394 | 1151 | 767 | 2312 |
| 2014-06-29 07:59:22 | 406 | 1151 | 767 | 2324 |
| 2014-06-30 07:59:58 | 18909 | 18012 | 20306 | 57227 |
| 2014-07-01 07:59:59 | 17736 | 16951 | 19213 | 53900 |
| 2014-07-02 07:59:48 | 19088 | 18310 | 21040 | 58438 |
| 2014-07-03 07:59:49 | 19842 | 19024 | 21490 | 60356 |
+---------------------+-----------+-----------+-----------+-------------+
第二选择声明：
SELECT rec.time_stamp,
rec.day_chan1,
rec.day_chan2,
rec.day_chan3,
rec.total_phase
FROM
(SELECT ".$this->table_name.".*,
DATE(time_stamp) AS mydate,
TIME(time_stamp) AS mytime
FROM ".$this->table_name."
WHERE TIME(time_stamp) >= '00:00:00'
AND TIME(time_stamp) <= '07:59:59') AS rec
JOIN
(SELECT DATE(time_stamp) AS mydate,
MAX(TIME(time_stamp)) AS mytime
FROM ".$this->table_name."
WHERE TIME(time_stamp) >= '00:00:00'
AND TIME(time_stamp) <= '07:59:59'
GROUP BY DATE(time_stamp)) AS max_times ON max_times.mydate = rec.mydate
AND max_times.mytime = rec.mytime
ORDER BY rec.mydate
结果：
+---------------------+-----------+-----------+-----------+-------------+
| time_stamp | day_chan1 | day_chan2 | day_chan3 | total_phase |
+---------------------+-----------+-----------+-----------+-------------+
| 2014-06-03 07:59:48 | 24210 | 22744 | 26003 | 72957 |
| 2014-06-04 07:59:49 | 112603 | 103417 | 121368 | 337388 |
| 2014-06-05 07:59:50 | 21302 | 20165 | 23317 | 64784 |
| 2014-06-06 07:59:50 | 21561 | 20951 | 23875 | 66387 |
| 2014-06-07 07:59:03 | 408 | 1151 | 767 | 2326 |
| 2014-06-08 07:59:04 | 384 | 1151 | 767 | 2302 |
| 2014-06-09 07:59:53 | 21580 | 20656 | 23788 | 66024 |
| 2014-06-10 07:59:54 | 19689 | 18861 | 21657 | 60207 |
| 2014-06-11 07:59:54 | 22283 | 21132 | 24820 | 68235 |
| 2014-06-12 07:59:56 | 20489 | 19327 | 22377 | 62193 |
| 2014-06-13 07:59:56 | 20646 | 19485 | 22504 | 62635 |
| 2014-06-15 07:59:09 | 387 | 1151 | 767 | 2305 |
| 2014-06-16 07:59:58 | 30681 | 29050 | 33593 | 93324 |
| 2014-06-17 07:59:59 | 18248 | 17701 | 20432 | 56381 |
| 2014-06-18 07:37:49 | 40170 | 38123 | 47013 | 125306 |
| 2014-06-19 07:59:38 | 22417 | 21001 | 24484 | 67902 |
| 2014-06-20 07:59:50 | 19104 | 18238 | 21007 | 58349 |
| 2014-06-21 07:59:15 | 384 | 1151 | 767 | 2302 |
| 2014-06-22 07:59:16 | 384 | 1151 | 767 | 2302 |
| 2014-06-23 07:59:53 | 19675 | 18582 | 21114 | 59371 |
| 2014-06-24 07:59:42 | 18341 | 17504 | 19427 | 55272 |
| 2014-06-25 07:59:55 | 19554 | 18469 | 20879 | 58902 |
| 2014-06-26 07:59:55 | 20241 | 19262 | 21881 | 61384 |
| 2014-06-27 07:59:56 | 17984 | 17033 | 19528 | 54545 |
| 2014-06-28 07:59:21 | 394 | 1151 | 767 | 2312 |
| 2014-06-29 07:59:22 | 406 | 1151 | 767 | 2324 |
| 2014-06-30 07:59:58 | 18909 | 18012 | 20306 | 57227 |
| 2014-07-01 07:59:59 | 17736 | 16951 | 19213 | 53900 |
| 2014-07-02 07:59:48 | 19088 | 18310 | 21040 | 58438 |
| 2014-07-03 07:59:49 | 19842 | 19024 | 21490 | 60356 |
+---------------------+-----------+-----------+-----------+-------------+
现在我需要减去第一个 - 第二个声明。
我尝试了这个，但它不起作用：
SELECT *
FROM (
(SELECT rec.time_stamp,
rec.day_chan1,
rec.day_chan2,
rec.day_chan3,
rec.total_phase
FROM
(SELECT ".$this->table_name.".*,
DATE(time_stamp) AS mydate,
TIME(time_stamp) AS mytime
FROM ".$this->table_name."
WHERE TIME(time_stamp) >= '08:00:00'
AND TIME(time_stamp) <= '16:59:59') AS rec
JOIN
(SELECT DATE(time_stamp) AS mydate,
MAX(TIME(time_stamp)) AS mytime
FROM ".$this->table_name."
WHERE TIME(time_stamp) >= '08:00:00'
AND TIME(time_stamp) <= '16:59:59'
GROUP BY DATE(time_stamp)) AS max_times ON max_times.mydate = rec.mydate
AND max_times.mytime = rec.mytime
ORDER BY rec.mydate) -
(SELECT rec.time_stamp,
rec.day_chan1,
rec.day_chan2,
rec.day_chan3,
rec.total_phase
FROM
(SELECT ".$this->table_name.".*,
DATE(time_stamp) AS mydate,
TIME(time_stamp) AS mytime
FROM ".$this->table_name."
WHERE TIME(time_stamp) >= '00:00:00'
AND TIME(time_stamp) <= '07:59:59') AS rec
JOIN
(SELECT DATE(time_stamp) AS mydate,
MAX(TIME(time_stamp)) AS mytime
FROM ".$this->table_name."
WHERE TIME(time_stamp) >= '00:00:00'
AND TIME(time_stamp) <= '07:59:59'
GROUP BY DATE(time_stamp)) AS max_times ON max_times.mydate = rec.mydate
AND max_times.mytime = rec.mytime
ORDER BY rec.mydate))
答案 0 :(得分：1)
使用左连接，如解释：here
不幸的是，MySQL没有其他DBMS那样的关系减法运算符，所以你应该像下面的例子中解释的那样：
解决方案Oracle
SELECT x, y FROM table_a
MINUS
SELECT x, y FROM table_b;
解决方案MySQL
SELECT a.x, a.y
FROM table_a a LEFT JOIN table_b b
ON a.x = b.x AND a.y = b.y
WHERE b.x IS NULL;