Mysql 如何优化子查询

我有一个包含多个子查询的查询，根据状态统计某个事务中涉及的用户数

SELECT * FROM (
    SELECT
    DATE(changes.created_at) AS `date`,
    SUM(IF(changes.status = 15, 1, 0)) AS installed_daily,
    SUM(IF(changes.status = 3, 1, 0)) AS port_reserved,
    (
      SELECT COUNT(DISTINCT created_by) FROM applicant_state_changes
      WHERE DATE(created_at) = DATE(changes.created_at) AND status = 3
    ) AS user_port_reserved,
    SUM(IF(changes.status = 5, 1, 0)) AS document_validated,
    (
      SELECT COUNT(DISTINCT created_by) FROM applicant_state_changes
      WHERE DATE(created_at) = DATE(changes.created_at) AND status = 5
    ) AS user_document_validated,
    SUM(IF(changes.status = 7, 1, 0)) AS account_created,
    (
      SELECT COUNT(DISTINCT created_by) FROM applicant_state_changes
      WHERE DATE(created_at) = DATE(changes.created_at) AND status = 7
    ) AS user_account_created,
    SUM(IF(changes.status = 11, 1, 0)) AS jo_created,
    (
      SELECT COUNT(DISTINCT created_by) FROM applicant_state_changes
      WHERE DATE(created_at) = DATE(changes.created_at) AND status = 11
    ) AS user_jo_created
    FROM applicant_state_changes AS changes
    GROUP BY DATE(changes.created_at)
    LIMIT 100 OFFSET 0
) a
ORDER BY date ASC;

---

这大约需要130秒。如果没有子查询，我的查询只需要0.5秒。

您可以使用case when表达式使用条件聚合

 SELECT
    DATE(changes.created_at) AS `date`,
    SUM(IF(changes.status = 15, 1, 0)) AS installed_daily,
    SUM(IF(changes.status = 3, 1, 0)) AS port_reserved,
    count(distinct case when status = 3 then created_by end) as user_port_reserved
    ,
    SUM(IF(changes.status = 5, 1, 0)) AS document_validated,
    count(distinct case when status = 5 then created_by  end) AS user_document_validated,
    SUM(IF(changes.status = 7, 1, 0)) AS account_created,
    count(distinct case when status = 7 then 1 end) AS user_account_created,
    SUM(IF(changes.status = 11, 1, 0)) AS jo_created,
    count(distinct case when status = 11 then created_by  end) AS user_jo_created
    FROM applicant_state_changes AS changes where 
    GROUP BY DATE(changes.created_at)
    LIMIT 100 OFFSET 0

---

问题是我正在计算由创建的不同值。@SeeMore，我已经更改了它-您现在可以检查谢谢。结果持续时间现在为0.5秒。