why mysql query select from two tables by " IN " is slow query

Question

i have a two table contains customer id like this :

(SELECT * FROM customers WHERE cellular = '$cellular' OR  id  IN(SELECT customer FROM clients WHERE number=$cellular  ) )

when i search for customer cellular client OR cellular this mysql query take a 30 seconds . how i can to be more fast?

Answer 1

Try MySQL join

SELECT * FROM customers left join clients 
on customers.id=clients.customer 
where clients.number=$cellular or customers.cellular = '$cellular'

or try this query :-

SELECT * FROM customers inner join clients 
on customers.id=clients.customer 
where clients.number=$cellular or customers.cellular = '$cellular'