我有下表,其中状态 0 表示非事件设备,状态 1 表示事件设备。
CREATE TABLE `devices` (
`id` int NOT NULL AUTO_INCREMENT,
`state` int unsigned NOT NULL,
`dt` datetime NOT NULL,
`name` varchar(60) COLLATE utf8_unicode_ci DEFAULT NULL,
PRIMARY KEY (id)
) ENGINE=InnoDB DEFAULT CHARSET=utf8 COLLATE=utf8_unicode_ci;
INSERT INTO devices (state,name,dt) VALUES (1,'Alfa','2021-10-12 11:30:00');
INSERT INTO devices (state,name,dt) VALUES (0,'Alfa','2021-10-12 11:40:00');
INSERT INTO devices (state,name,dt) VALUES (1,'Alfa','2021-10-12 11:50:00');
INSERT INTO devices (state,name,dt) VALUES (1,'Alfa','2021-10-12 12:00:00');
INSERT INTO devices (state,name,dt) VALUES (1,'Beta','2021-10-12 11:30:00');
INSERT INTO devices (state,name,dt) VALUES (0,'Beta','2021-10-12 11:40:00');
INSERT INTO devices (state,name,dt) VALUES (0,'Beta','2021-10-12 11:50:00');
INSERT INTO devices (state,name,dt) VALUES (0,'Beta','2021-10-12 12:00:00');
http://sqlfiddle.com/#!9/8ea07de/3
查询的预期结果是:
Name State FROM TO
Alfa 1 '2021-10-12 11:50:00' '2021-10-12 12:00:00'
Beta 0 '2021-10-12 11:40:00' '2021-10-12 12:00:00'
目前我只能获取“name”、“to”和“state”列。 对于 MySQL 5.6,是否可以找到具有预期结果(“来自”列)的查询?
最佳答案
您可以使用下一个查询:
SET @state = -1; -- initial value not equal to real values
SET @dt = ''; -- initial value not equal to real dates
SELECT
name,
state,
from_dt,
dt
FROM (
-- get last dt by name
SELECT name, max(dt) dt
FROM devices
GROUP BY name
) last_state
JOIN (
SELECT
name,
state,
dt,
-- store dt eachtime when state changes
@dt := IF(@state <> state, dt, @dt) from_dt,
@state := state
FROM devices
ORDER BY name, dt ASC
) first_state using (name, dt)
;
关于mysql - 查找mysql中最后一个序列的开始时间,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/69556831/