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基本上我有 4 个表和当前组的组 ID。我将列出重要的字段和信息：

Users:
ID,
FirstName,
LastName

Groups:
ID,
participantlist_id

participantlist:
list_id

participantlist_links:
list_id,
participant_id

我已经想出了如何用一个小函数在树的最高点显示参与者列表中的所有用户：

SELECT Users.ID,Users.FirstName,Users.LastName FROM Users
JOIN participantlist_links ON Users.ID = participantlist_links.participant_id
JOIN participantlist ON participantlist_links.list_id = participantlist.list_id
JOIN Groups ON participantlist.list_id = Groups.participantlist_id AND 
Groups.ID = '".workspaces_tell_me_brainstorm_group_id_from_group_id($group_id)."'

现在我想排除所有链接到当前组的参与者列表.list_id ($group_id) 的用户，但我只是想不出一个在单个查询中完成所有操作的好方法。我认为解决方案将是某种左连接/右连接或左/右外连接比较。

我的临时工作但非常耗时的解决方案是：

SELECT table2.id as ID, table2.firstname as FirstName, table2.lastname as LastName
FROM

(SELECT table1.ID,table1.FirstName,table1.LastName FROM Users as table1
JOIN participantlist_links ON table1.ID = participantlist_links.participant_id
JOIN participantlist ON participantlist_links.list_id = participantlist.list_id
JOIN Groups ON participantlist.list_id = Groups.participantlist_id 
AND Groups.ID = '".workspaces_tell_me_brainstorm_group_id_from_group_id($group_id)."')
as table2

LEFT JOIN
(SELECT table4.ID,table4.FirstName,table4.LastName FROM Users as table4
JOIN participantlist_links ON table4.ID = participantlist_links.participant_id
JOIN participantlist ON participantlist_links.list_id = participantlist.list_id
JOIN Groups ON participantlist.list_id = Groups.participantlist_id 
AND Groups.ID = '".$group_id."') 
as table3

ON table2.ID = table3.ID WHERE table3.id is null

有什么建议么？

4

1 回答 1

1

我会去做一些更简单的事情。

我想not in是你的朋友在这里。它应该使您的代码更易于阅读，并且很可能会让 mysql 对其进行更多优化：

SELECT table1.ID,
       table1.FirstName,
       table1.LastName 
  FROM Users as table1
  JOIN participantlist_links ON table1.ID = participantlist_links.participant_id
  JOIN participantlist ON participantlist_links.list_id = participantlist.list_id
  JOIN Groups ON participantlist.list_id = Groups.participantlist_id 
   AND Groups.ID = '".workspaces_tell_me_brainstorm_group_id_from_group_id($group_id)."')
   AND table1.id not in (
               SELECT table4.ID
                 FROM Users as table4
                 JOIN participantlist_links ON table4.ID = participantlist_links.participant_id
                 JOIN participantlist ON participantlist_links.list_id = participantlist.list_id
                 JOIN Groups ON participantlist.list_id = Groups.participantlist_id 
                  AND Groups.ID = '".$group_id."'
                )
于 2012-05-19T13:59:25.440 回答