Question

有人可以帮我解决如何使用OR向一个查询添加几个不同的查询吗？

我有一些帖子，我只想向用户显示允许查看的帖子或允许查看的帖子或每个帖子。

SELECT p.*, c.name, cb.categoryId FROM Posts AS p
LEFT JOIN CategoryBindings AS cb ON cb.postId = p.id
LEFT JOIN Categories AS c ON c.id = cb.categoryId
LEFT JOIN UserBindings AS ub ON ub.postId = p.id
WHERE ub.userId = 1

SELECT p.*, c.name, cb.categoryId FROM Posts AS p
LEFT JOIN CategoryBindings AS cb ON cb.postId = p.id
LEFT JOIN Categories AS c ON c.id = cb.categoryId
LEFT JOIN GroupPostBindings AS gpb ON gpb.postId = p.id
LEFT JOIN GroupBindings AS gp ON gp.groupId = gpb.groupId
WHERE gp.userId = 1

SELECT p.*, c.name, cb.categoryId FROM Posts AS p
LEFT JOIN CategoryBindings AS cb ON cb.postId = p.id
LEFT JOIN Categories AS c ON c.id = cb.categoryId
WHERE p.public = 1

如何将这三个查询添加到一个查询中？

Answer 1

SELECT p.*, c.name, cb.categoryId FROM Posts AS p
LEFT JOIN CategoryBindings AS cb ON cb.postId = p.id
LEFT JOIN Categories AS c ON c.id = cb.categoryId
LEFT JOIN UserBindings AS ub ON ub.postId = p.id
LEFT JOIN GroupPostBindings AS gpb ON gpb.postId = p.id
LEFT JOIN GroupBindings AS gp ON gp.groupId = gpb.groupId
where p.public = 1 or ub.userId = 1 or gp.userId = 1

应该有效，假设您的连接将始终返回一个值（看起来为0或1），而不是排除行

Answer 2

您是否考虑过使用UNION？无可否认，这可能是一种更有效的方式 - 这只是我想到的第一件事。

MySQL使用OR执行多个查询

2 个答案: