Cannot create trigger if-delete-clause - sql

Question

Here is the code I have
CREATE TRIGGER free_tokens AFTER INSERT ON `csrf_token`
IF (SELECT COUNT(`csrf_token`.`id`)) > 5000 THEN
DELETE FROM `csrf_token` WHERE `csrf_token`.`time` < (UNIX_TIMESTAMP(NOW() - INTERVAL 2 HOUR))
END IF;
which checks if there is more than 5000 entries after an insert, then deletes all entries which are greater than 2 hours old
I am getting you have an error in your mysql syntax near IF (SELECT ... DELETE FROM ...
I am using MariaDB, can someone help me understand where is the error in this simple statement?

Answer 1

There are small things that your trigger definition is missing:
change the MariaDB delimiter type into '//', so that the trigger instructions can be separated by the semicolon instead
FOR EACH ROW, as part of MariaDB trigger syntax
your DELETE statement is missing a semicolon at the end
can't nest queries inside an IF-THEN-ELSE statement
END to delimit the end of the trigger after its definition, as part of MariaDB syntax
A workaround for the nested query in your IF statement can be to define a variable to be updated with the result of a SELECT, to be carried out before the IF statement.
DELIMITER //
CREATE OR REPLACE TRIGGER free_tokens
AFTER INSERT
ON `csrf_token`
FOR EACH ROW
BEGIN
DECLARE num_rows INT;
SELECT
COUNT(*) INTO num_rows
FROM
`csrf_token`;
IF num_rows > 5000 THEN
DELETE FROM
`csrf_token`
WHERE
`csrf_token`.`time` < (UNIX_TIMESTAMP(NOW() - INTERVAL 2 HOUR));
END IF;
END//
DELIMITER ;
More on MariaDB trigger syntax here.