MySQL error in trigger syntax

Question

I'm trying to create a trigger to allow only one line per table. This database will be used by more than one software so I would like this automation to be done by the database.

Before the insert, the database should clean the previous register, plus the foreign tables.

At the moment I'm trying to clean the current table, but I'm having syntax errors

EDIT:

Adding a semicolon on DELETE FROM sensor;

Answer 1

Try removing the begin/end:

CREATE TRIGGER before_insert_sensor BEFORE INSERT ON `sensor`
FOR EACH ROW
DELETE FROM sensor;

You might encounter issues trying to delete during the insert, though.