我有5张桌子:
tag: {tagID,tagDetails}
user: {userID,userDetails,u_status=[active or banned]}
subscribe: {tagID,userID}
item: {itemID, itemDetails,i_status=[active or banned]}
item_tag: {tagID,itemID}
我想选择这些数据:
result: {tagID, tagDetails, num_subscribers, num_items}
对于每个标记ID,num_subscribers是表用户下其u_status为“活动”并且其用户ID和所述标记ID存在于表subscribe中的用户数。
对于每个tagID,num_items是表项下其i_status为“活动”并且其itemID和所述tagID存在于表item_tag中的用户数
另外,我希望所有的tagID都出现在结果中。如果没有用户订阅或与该tagID相关联的项目,则记录为
{tagID,tagDetails,0,0}
产生此结果的最佳嵌套查询(最好是“人类可读”)是什么?
最佳答案
这是你所追求的吗?
SELECT T.tagID, T.tagDetails, count(distinct U.u_status), count(distinct I.i_status)
FROM tag T
JOIN subscribe S ON T.tagID = S.tagID
JOIN user U ON S.userID = U.userID
JOIN item_tag IT ON T.tagID = IT.tagID
JOIN item I ON IT.itemID = I.itemID
WHERE U.u_status = 'active' and I.i_status = 'active'
GROUP BY T.tagID
UNION
(SELECT tagID, tagDetails, 0, 0
FROM tag
EXCEPT
SELECT T.tagID, T.tagDetails, 0, 0
FROM tag T
JOIN subscribe S ON T.tagID = S.tagID
JOIN user U ON S.userID = U.userID
JOIN item_tag IT ON T.tagID = IT.tagID
JOIN item I ON IT.itemID = I.itemID
WHERE U.u_status = 'active' and I.i_status = 'active'
GROUP BY T.tagID)
您可能不得不摆弄括号和别名。
关于mysql - MySQL查询从5个表中选择联接,我们在Stack Overflow上找到一个类似的问题:https://stackoverflow.com/questions/12669430/