How to check if created_in column is inside trigger?

Question

Column and trigger structures in user tables

CREATE TABLE `users` (
 `created_in` datetime NOT NULL
) ENGINE=InnoDB DEFAULT CHARSET=utf8 COLLATE=utf8_unicode_ci

trigger	event	sheet	statement	time
...	insert	user	IF NEW.created_in = "" THEN SIGNAL SQLSTATE "45000"; IF END	Before

I'm trying to cancel the insert if the created_in column isn't there but that doesn't work.

How to check whether the created_in column is none?

MySQL version is 5.7

Answer 1

No trigger is required, session strict mode is enough:

db<>violinhere