Не существует действенного способа сделать это без оконных функций в MySql версиях до 8.0. Один из способов - получить для каждой строки максимальное значение cDate до текущей cDate для того же значения cRt:
SELECT t.*,
ROUND(time_to_sec((TIMEDIFF(
t.cDate,
(SELECT MAX(cDate) FROM tablename WHERE cRt = t.cRt AND cDate < t.cDate)
))) / 60) AS td
FROM tablename t
См. Демонстрационную версию . Если вы можете использовать LAG()
оконную функцию:
SELECT *,
ROUND(time_to_sec((TIMEDIFF(
cDate,
LAG(cDate) OVER (PARTITION BY cRt ORDER BY cDate)
))) / 60) AS td
FROM tablename
См. demo .
Результаты:
| cNode | cEl | cDate | cEvent | cRt | td |
| ------------- | -------- | ------------------- | -------------------------- | -------- | ----- |
| SD20-2-100102 | SD100102 | 2020-04-13 11:34:35 | POSITIVE REMOTE CONTROL SN | SD100102 | 259 |
| SD20-2-100102 | SD100102 | 2020-04-13 07:15:14 | NEGATIVE REMOTE CONTROL SN | SD100102 | |
| SD40-2-103423 | SD103423 | 2020-04-06 06:21:50 | POSITIVE REMOTE CONTROL SN | SD103423 | 1 |
| SD40-2-103423 | SD103423 | 2020-04-06 06:20:21 | NEGATIVE REMOTE CONTROL SN | SD103423 | |
| SD20-2-103484 | SD103484 | 2020-04-23 15:19:37 | POSITIVE REMOTE CONTROL SN | SD103484 | 2 |
| SD20-2-103484 | SD103484 | 2020-04-23 15:17:53 | NEGATIVE REMOTE CONTROL SN | SD103484 | 2928 |
| SD20-2-103484 | SD103484 | 2020-04-21 14:29:50 | POSITIVE REMOTE CONTROL SN | SD103484 | 10 |
| SD20-2-103484 | SD103484 | 2020-04-21 14:19:50 | NEGATIVE REMOTE CONTROL SN | SD103484 | 50340 |
| SD20-2-103484 | SD103484 | 2020-02-13 07:33:00 | POSITIVE REMOTE CONTROL SN | SD103484 | 1 |
| SD20-2-103484 | SD103484 | 2020-02-13 07:31:55 | NEGATIVE REMOTE CONTROL SN | SD103484 | 44135 |
| SD20-2-103484 | SD103484 | 2020-01-13 15:57:16 | POSITIVE REMOTE CONTROL SN | SD103484 | 2386 |
| SD20-2-103484 | SD103484 | 2020-01-12 00:10:50 | NEGATIVE REMOTE CONTROL SN | SD103484 | |
| SD40-2-103565 | SD103565 | 2020-04-07 12:20:48 | POSITIVE REMOTE CONTROL SN | SD103565 | 21 |
| SD40-2-103565 | SD103565 | 2020-04-07 11:59:47 | NEGATIVE REMOTE CONTROL SN | SD103565 | 47534 |
| SD40-2-103565 | SD103565 | 2020-03-05 11:46:03 | POSITIVE REMOTE CONTROL SN | SD103565 | 152 |
| SD40-2-103565 | SD103565 | 2020-03-05 09:13:46 | NEGATIVE REMOTE CONTROL SN | SD103565 | 22843 |
| SD40-2-103565 | SD103565 | 2020-02-18 12:30:21 | POSITIVE REMOTE CONTROL SN | SD103565 | 1 |
| SD40-2-103565 | SD103565 | 2020-02-18 12:29:12 | NEGATIVE REMOTE CONTROL SN | SD103565 | 6037 |
| SD40-2-103565 | SD103565 | 2020-02-14 07:52:28 | POSITIVE REMOTE CONTROL SN | SD103565 | 2 |
| SD40-2-103565 | SD103565 | 2020-02-14 07:50:42 | NEGATIVE REMOTE CONTROL SN | SD103565 | |