为什么mysql查询通过“IN”从两个表中选择是慢查询

Question

我有两个表包含这样的客户ID：

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

当我搜索客户蜂窝客户端或蜂窝时，这个mysql查询需要30秒。 我怎么能更快？

Answer 1

尝试MySQL join

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

或尝试此查询： -

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