Question

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

我已经想出如何在树的最高点显示参与者list.list_id中的所有用户，但功能有点：

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)."'

现在我想排除链接到当前组（$ group_id）的participantlist.list_id的所有用户，但我无法找到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/右或左/右外连接比较。

我的工作暂时，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

有什么建议吗？

Answer 1

我会选择更简单的东西。

我认为not in是你的朋友。它应该让你的代码更容易阅读，并且很可能让mysql更优化它：

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."'
                )

混淆了mysql中复杂的连接请求

1 个答案: