为什么这个sql加了where条件反而更加慢了呢，慢了5s左右

Question

SELECT COUNT(1) FROM ( SELECT
    c.id,
    per_num,
    per_name,
    per_nation,
    per_sex,
    per_phone,
    per_birthday
FROM
    t_cab_cer_info c
    LEFT JOIN (
    SELECT
    device_id,
    cer_id,
    ticketbox_num,
    operate_type
    FROM
    t_cab_cer_operation 


   where 
    operate_type = '1'


    ) temp ON c.id = temp.cer_id   
     ) total
     ```

Answer 1

1、你的检索字段是否命中索引；
2、operate_type的数据类型和传参的类型是否一致；