MySQL: UPDATE query based on SELECT query

update tableA a
left join tableB b on
    a.name_a = b.name_b
set
    validation_check = if(start_dts > end_dts, 'VALID', '')
UPDATE payments p 
    INNER JOIN users u ON
    p.pay_id=u.user_id
SET 
    p.pay_email=u.user_email, 
    p.pay_firstname=u.user_firstname, 
    p.pay_lastname=u.user_lastname, 
    p.pay_date=u.user_date