mysql常量区间交集

触发器是可以的,但是为了证明不需要触发器,请考虑以下几点…

DROP TABLE IF EXISTS my_table;

CREATE TABLE my_table (
  id SERIAL,
  dt_from DATE NOT NULL,
  dt_to DATE NOT NULL,
  PRIMARY KEY (id)
);

INSERT INTO my_table (dt_from,dt_to)
VALUES
('2018-05-31','2018-06-03');

--尝试1:日期冲突

SET @dt_from = '2018-05-28';
SET @dt_to = '2018-06-01';

INSERT INTO my_table (dt_from,dt_to) 
SELECT @dt_from
     , @dt_to
  FROM (SELECT 1) x
  LEFT 
  JOIN my_table y 
    ON y.dt_from < @dt_to 
   AND y.dt_to > @dt_from 
 WHERE y.id IS NULL;

--尝试2:不冲突的日期

SET @dt_from = '2018-06-04'; 
SET @dt_to = '2018-06-06'; 

INSERT INTO my_table (dt_from,dt_to) 
SELECT @dt_from
     , @dt_to
  FROM (SELECT 1) x
  LEFT 
  JOIN my_table y 
    ON y.dt_from < @dt_to 
   AND y.dt_to > @dt_from 
 WHERE y.id IS NULL;

 SELECT * FROM my_table;
+----+------------+------------+
| id | dt_from    | dt_to      |
+----+------------+------------+
|  1 | 2018-05-31 | 2018-06-03 |
|  2 | 2018-06-04 | 2018-06-06 |
+----+------------+------------+

看。冲突日期将被忽略。