Sql 计算所有子项仅属于特定类型的父项类型
一个项目可以有很多成就;一项成就只能有一个项目 到目前为止,我有一个非常基本的查询,但我不太熟悉子查询或最有效的方法。我试着按状态统计一个项目的所有成就,然后试着做数学计算,看看状态3是否等于成就总数,但这感觉非常有效 以下是我目前拥有的:Sql 计算所有子项仅属于特定类型的父项类型,sql,database,performance,psql,Sql,Database,Performance,Psql,一个项目可以有很多成就;一项成就只能有一个项目 到目前为止,我有一个非常基本的查询,但我不太熟悉子查询或最有效的方法。我试着按状态统计一个项目的所有成就,然后试着做数学计算,看看状态3是否等于成就总数,但这感觉非常有效 以下是我目前拥有的: Project Accomplishment ------- --------------- id id project_name accomplishme
Project Accomplishment
------- ---------------
id id
project_name accomplishment_name
project_status_id project_id
accomplishment_status_id
我希望输出显示所有项目的Project_ID和Project_name,这些项目的所有关联成就状态都为3
示例数据:
SELECT p.id, p.name, COUNT(a) AS active_accomp_count FROM habits4.accomplishment a
join habits4.project p ON p.id = a.project_id
WHERE a.accomp_status_id = 1
GROUP BY p.id
SELECT p.id, p.name, count(a) AS completed_accomp_count FROM habits4.accomplishment a
JOIN habits4.project p ON p.id = a.project_id
WHERE a.accomp_status_id = 2
GROUP BY p.id
SELECT p.id, p.name, COUNT(a) AS inactive_accomp_count FROM habits4.accomplishment a
JOIN habits4.project p ON p.id = a.project_id
WHERE a.accomp_status_id = 3
GROUP BY p.id
成就4
状态=3
`
项目2应该显示在输出中,因为它只有状态为3的成就。
项目1不应显示在输出中,因为尽管它确实具有状态为3的成就,但它也具有状态为3以外的成就。因此您希望项目满足两个条件
状态=3
Project 1 Project 2
----------------- -----------------
Accomplishment 1 Accomplishment 5
status = 1 status = 3
Accomplishment 2 Accomplishment 6
status = 1 status = 3
Accomplishment 3
status = 2
然后将其与状态为3的项目所需的内部连接相结合
SELECT p.id, p.name, COUNT(a) AS inactive_accomp_count
FROM habits4.project p
LEFT OUTER JOIN habits4.accomplishment a ON p.id = a.project_id
WHERE a.id IS NULL
GROUP BY p.id, p.name
因此,我们一起:
SELECT p.id, p.name, COUNT(a) AS inactive_accomp_count
FROM habits4.project p
INNER JOIN habits4.accomplishment a ON p.id = a.project_id
WHERE a.accomp_status_id = 3
这将为您提供正确的项目,但计数将混乱,因为我们在记录组中做了太多。因此,将其用作子选择,并编写外部查询以正确计数记录。就是这样!不知道我为什么要间隔内部连接--谢谢你的帮助!
SELECT p.id AS inactive_accomp_count
FROM habits4.project p1
INNER JOIN habits4.accomplishment a1 ON p1.id = a1.project_id
INNER JOIN habits4.project p2 ON p1.id = p2.id
LEFT OUTER JOIN habits4.accomplishment a2 ON p2.id = a2.project_id
WHERE a2.id IS NULL
GROUP BY p1.id