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
Via: stackoverflow.com