我有一个复杂的查询,其中包含大量的内连接和左连接,我正在尝试使用 SQL 的 COUNT 函数获取某个表中的记录数。
我正在尝试使用 proposal_id 获取每个提案的“held_proposals”表中的记录数,因为我将使用 foreach 循环将数据输出到表中。
本质上,我想显示有多少学生“持有”反对每个提案的提案。
这是我的尝试:
SELECT p.proposal_id, p.proposal_title, p.description, u.user_record_id, u.forename, u.surname, c.course_title, h.*,
GROUP_CONCAT(DISTINCT t.tag_title) AS tags FROM proposal p
LEFT JOIN user u on u.user_record_id = p.user_record_id
LEFT JOIN course_details c on c.course_code = p.course_code
LEFT JOIN record r on r.proposal_id = p.proposal_id
LEFT JOIN proposal_tags pt on pt.proposal_id = p.proposal_id
LEFT JOIN tag_details t on t.tag_code = pt.tag_code
LEFT JOIN (
SELECT h.student_record_id, COUNT(*) AS Held
FROM held_proposals h
) H on h.proposal_id = p.proposal_id
WHERE p.source = "Supervisor"
AND (r.status_code not in (3,8) OR r.status_code IS NULL)
GROUP BY p.proposal_id;
表格目前看起来像这样:
我想在表的末尾添加从“held_proposals”表返回的每个提案的值作为另一列。
能否就如何在 SQL 查询中实现此目的向我提供一些指导。提前谢谢你。
最佳答案
您需要将要加入的查询中的计数分组为
SELECT
p.proposal_id,
p.proposal_title,
p.description,
u.user_record_id,
u.forename,
u.surname,
c.course_title, coalesce(h.Held,0) as `Held`,
GROUP_CONCAT(DISTINCT t.tag_title) AS tags
FROM proposal p
LEFT JOIN user u on u.user_record_id = p.user_record_id
LEFT JOIN course_details c on c.course_code = p.course_code
LEFT JOIN record r on r.proposal_id = p.proposal_id
LEFT JOIN proposal_tags pt on pt.proposal_id = p.proposal_id
LEFT JOIN tag_details t on t.tag_code = pt.tag_code
LEFT JOIN (
SELECT proposal_id, COUNT(*) AS Held
FROM held_proposals group by proposal_id
) h on h.proposal_id = p.proposal_id
WHERE p.source = "Supervisor"
AND (r.status_code not in (3,8) OR r.status_code IS NULL)
GROUP BY p.proposal_id;
关于php - 尝试将计数函数添加到复杂查询 PHP MYSQL,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/29695706/