我遇到了JOIN需要更多时间的查询，我想用WHERE EXISTS代替JOIN，因为明智的表现EXISTS比sub query's columns花费更少的时间它
我修改了查询并按预期执行但我无法在主查询中使用query
这是我的SELECT MAX(st.grade_level::integer) AS grades ,
scl.sid AS org_sourced_id
FROM schedules_53b055b75cd237fde3af904c1e726e12 sch
LEFT JOIN schools scl ON(sch.school_id=scl.school_id)
AND scl.batch_id=sch.batch_id
AND scl.client_id = sch.client_id
AND sch.run_id = scl.run_id
WHERE EXISTS
(SELECT t.term_id,t.abbreviation
FROM terms t
WHERE (sch.term = t.term_id)
AND t.batch_id=sch.batch_id
AND t.client_id = sch.client_id
AND t.run_id = sch.run_id)
AND EXISTS
(SELECT st.grade_level,
st.sid
FROM students st
WHERE (sch.student_id=st.sid)
AND st.batch_id= sch.batch_id
AND st.client_id = sch.client_id
AND st.run_id = sch.run_id)
GROUP BY scl.sid ,
sch.course_name ,
sch.course_number,
sch.school_id
ERROR: missing FROM-clause entry for table "st"
SQL state: 42P01
Character: 29
我收到了这个错误：
sub query我这里仅使用一列作为样本，但我必须使用EXISTS中的更多字段。
我的主要目标是如何使用pg或任何更优化的替代解决方案来实现这一目标
我在Node.js使用Node.js模块，因为后端我正在使用JOIN。
更新
使用SELECT MAX(st.grade_level::integer) AS grades ,
scl.sid AS org_sourced_id
FROM schedules_53b055b75cd237fde3af904c1e726e12 sch
LEFT JOIN schools scl ON(sch.school_id=scl.school_id)
AND scl.batch_id=sch.batch_id
AND scl.client_id = sch.client_id
AND sch.run_id = scl.run_id
LEFT JOIN terms t ON (sch.term = t.term_id)
AND t.batch_id=sch.batch_id
AND t.client_id = sch.client_id
AND t.run_id = sch.run_id
LEFT JOIN students st ON (sch.student_id=st.sid)
AND st.batch_id= sch.batch_id
AND st.client_id = sch.client_id
AND st.run_id = sch.run_id
GROUP BY scl.sid ,
sch.course_name ,
sch.course_number,
sch.school_id
@SET_MAKE@