Request sql for computed column (age)

Question

I have trouble with my computed column for calculate automatically age. I use latest version of Laragon, with HeidiSQL (11.2.06213).

See the request :

    CREATE TABLE client(
        id_client             Int  Auto_increment  NOT NULL ,
        
        client_date_naissance Date NOT NULL ,
       
        age    Int AS YEAR(NOW) - YEAR(client_date_naissance) 
    - (CASE WHEN MONTH(client_date_naissance) > MONTH(NOW) 
OR (MONTH(@client_date_naissance) = MONTH(NOW) 
AND DAY(client_date_naissance) > DAY(NOW)) THEN 1 ELSE END);
    
    ,CONSTRAINT client_PK PRIMARY KEY (id_client)
    )ENGINE=InnoDB;

I tried with "currendate" instead of "NOW", same with supressed the "int" for age.

In SQL's doc, i found this "TIMESTAMPDIFF(YEAR,birth,CURDATE()) " but doesn't work.

I precise , the meaning of "client_date_naissance" (french) is equal to birthday.

The error, for all case is :

Erreur SQL (1064) : 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 'YEAR(NOW) - YEAR(client_date_naissance) - (CASE WHEN MONTH(client_date_naissance'

Any ideas ? Thank for support.