我需要改善查询，特别是执行时间，这是我的查询：
SELECT SQL_CALC_FOUND_ROWS p.*,v.type,v.idName,v.name as etapaName,m.name AS manager,
c.name AS CLIENT,
(SELECT SEC_TO_TIME(SUM(TIME_TO_SEC(duration)))
FROM activities a
WHERE a.projectid = p.projectid) AS worked,
(SELECT SUM(TIME_TO_SEC(duration))
FROM activities a
WHERE a.projectid = p.projectid) AS worked_seconds,
(SELECT SUM(TIME_TO_SEC(remain_time))
FROM tasks t
WHERE t.projectid = p.projectid) AS remain_time
FROM projects p
INNER JOIN users m
ON p.managerid = m.userid
INNER JOIN clients c
ON p.clientid = c.clientid
INNER JOIN `values` v
ON p.etapa = v.id
WHERE 1 = 1
ORDER BY idName
ASC
该执行时间为aprox。 5秒如果我删除此部分：
(SELECT SUM(TIME_TO_SEC(remain_time)) FROM tasks t WHERE t.projectid = p.projectid) AS remain_time
执行时间减少到0.3秒。有没有一种方法可以获取rest_time的值以减少exec.time？
从PHP调用SQL（如果这与任何建议的解决方案有关）。
请您参考如下方法:
听起来您需要在tasks上建立索引。
尝试添加以下内容：
create index idx_tasks_projectid_remaintime on tasks(projectid, remain_time);
相关的子查询应该只使用索引并且执行得更快。
