为什么mysql查询通过“IN”从两个表中选择是慢查询

Question

我有一个包含客户 ID 的两张表，如下所示：

(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，此 mysql 查询需要 30 秒。 我怎样才能更快？

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'

或试试这个查询：-

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