Create user after insert in SQL table - mysql

Question

I want to create a new user with the same initial password every time I insert a row with the username in the table.
I tried but it doesn't work:
CREATE TABLE IF NOT EXISTS Professeur (
professeur_id int NOT NULL AUTO_INCREMENT,
prenom varchar(40) COLLATE utf8_bin NOT NULL,
name varchar(30) COLLATE utf8_bin NOT NULL,
titre char DEFAULT NULL,
PRIMARY KEY (professeur_id)
) ENGINE=InnoDB DEFAULT CHARSET=utf8 COLLATE=utf8_bin;
CREATE trigger trig_prof AFTER INSERT ON Professeur
FOR EACH ROW CREATE OR replace USER NEW.name#localhost identified BY pwd0;
ERROR:
ER_PARSE_ERROR: You have an error in your SQL syntax; check the manual that
corresponds to your MySQL server version for the right syntax to use near
'USER NEW.name#localhost identified BY pwd0' at line 2

Answer 1

Triggers have several limitations as described in the fine manual:
"Triggers cannot operate on any tables in the mysql, information_schema or performance_schema database."
Since users are stored in mysql schema (either in global_priv or user) this can't work.

Answer 2

Do things a different way...
Write a Stored Procedure that both creates the table and adds the user. See SQL SECURITY DEFINER for how to temporarily give an enduser root permission. But be aware of the security implications.
Then, to add the table and the user, it is one CALL statement.

Answer 3

Problem solved with a procedure as Rick James has suggested and with Prepared Statements https://dev.mysql.com/doc/refman/8.0/en/sql-prepared-statements.html
I put the following code in my script and I execute the source command SOURCE initdb_gestiondesnotes.SQL
After that I call the procedure with: CALL create_professeur();
DELIMITER $$
CREATE PROCEDURE CREATE_PROFESSEUR()
BEGIN
DECLARE v_a INT Default 1 ;
DECLARE v_nom VARCHAR(42);
DECLARE v_prenom VARCHAR(42);
DECLARE v_login VARCHAR(84);
DECLARE v_titre VARCHAR(5);
DECLARE v_pwd VARCHAR(5);
SET v_pwd = 'p';
simple_loop: LOOP
SET v_nom = CONCAT("prof", LPAD(CAST(v_a AS CHAR), 3, '0'));
SET v_prenom = CONCAT("prenom", LPAD(CAST(v_a AS CHAR), 3, '0'));
SET v_titre = CASE WHEN RAND() > .5
THEN 'M'
ELSE 'F' END;
INSERT INTO Professeur (prenom, nom, titre) VALUES (v_prenom, v_nom, v_titre);
SET v_login = CONCAT(v_prenom, v_nom);
SET #sql1 = CONCAT('CREATE OR REPLACE USER ', v_login, '#localhost identified BY \'p\' ');
PREPARE stm1 FROM #sql1;
EXECUTE stm1;
SET #sql2 = CONCAT('GRANT role_professeur TO ', v_login, '#localhost');
PREPARE stm2 FROM #sql2;
EXECUTE stm2;
SET #sql3 = CONCAT('SET DEFAULT ROLE role_professeur FOR ', v_login, '#localhost');
PREPARE stm3 FROM #sql3;
EXECUTE stm3;
SET v_a=v_a+1;
IF v_a=51 THEN
LEAVE simple_loop;
END IF;
END LOOP simple_loop;
DEALLOCATE PREPARE stm1;
DEALLOCATE PREPARE stm2;
DEALLOCATE PREPARE stm3;
END $$
DELIMITER ;
Now I hove 50 user with prenom001prof001, prenom002prof002... as login and 'p' as password. Again with prepared statements I gave each user the role of role_professeur.