Question

我有以下查询，我使用betwen运算符来获取具有特定数字之间年龄的记录，但查询花费了大量时间来显示结果，其中超过5分钟它还在运行

SELECT
  *,
  (SELECT COUNT(*)
   FROM users
   WHERE
     1=1 OR
     LOWER(age) BETWEEN 18 AND 20 OR
     LOWER(age) BETWEEN 20 AND 25 OR
     LOWER(age) BETWEEN 25 AND 30 OR
     LOWER(age) BETWEEN 30 AND 35
  ) AS totalcount
FROM users, states, countries, user_types, media
WHERE
  users.id_user_type = user_types.id AND
  users.id_state = states.id AND
  users.id_country = countries.id AND
  media.id_user = users.id AND
  media.profile_photo = 1 AND
  users.id_user_type = 3 OR
  LOWER(age) BETWEEN 18 AND 20 OR
  LOWER(age) BETWEEN 20 AND 25 OR
  LOWER(age) BETWEEN 25 AND 30 OR
  LOWER(age) BETWEEN 30 AND 35
ORDER BY users.id

令人不安的部分是：

LOWER(age) BETWEEN 18 AND 20 OR
LOWER(age) BETWEEN 20 AND 25 OR
LOWER(age) BETWEEN 25 AND 30 OR
LOWER(age) BETWEEN 30 AND 35

Answer 1

避免使用您拥有的or子句（这没有意义）。你的查询可能正在做很多CROSS JOIN操作，这就是为什么它花了太长时间（你的结果集是巨大的）。

 select *,
        (
            select count(*) 
              from users 
             where 1=1 
                or lower(age) between 18 and 20 
                or lower(age) between 20 and 25 
                or lower(age) between 25 and 30 
                or lower(age) between 30 and 35
        ) as totalcount 
   from users, states, countries, user_types, media 
  where users.id_user_type = user_types.id 
    and users.id_state = states.id 
    and users.id_country = countries.id 
    and media.id_user = users.id 
    and media.profile_photo = 1 
    and users.id_user_type = 3 
  order by users.id

此外，我们还不清楚您要使用此查询完成的操作。

回答这些问题可能会对我们有所帮助：

age列类型
您对内部查询的期望是什么

Answer 2

您的or语句分析不正确。你需要括号：

FROM users, states, countries, user_types, media
WHERE (users.id_user_type = user_types.id AND
       users.id_state = states.id AND
       users.id_country = countries.id AND
       media.id_user = users.id AND
       media.profile_photo = 1 AND
       (users.id_user_type = 3 OR
        LOWER(age) BETWEEN 18 AND 20 OR
        LOWER(age) BETWEEN 20 AND 25 OR
        LOWER(age) BETWEEN 25 AND 30 OR
        LOWER(age) BETWEEN 30 AND 35
       )

如上所述，您的查询必须在五个表中执行完整的笛卡尔积，然后进行一些奇怪的过滤。

如果使用正确的join语法，这基本上不是问题。简单规则：永远不要在from子句中使用逗号。

此外，查询似乎没有意义。为什么要将age存储为字符串（使用lower()建议？那么，为什么要将这些与整数进行比较？为什么要将连续范围分成四个不同的比较，而不是仅仅说age between 18 and 35？

查询需要很长时间才能执行

2 个答案: