困惑複雜加入在MySQL請求

Question

基本上我有4個表和當前組的組ID。 我將列出的重要領域和信息：

Users: 
ID, 
FirstName, 
LastName 

Groups: 
ID, 
participantlist_id 

participantlist: 
list_id 

participantlist_links: 
list_id, 
participant_id 

我已經想出如何證明是在樹的一個小功能，最高點participantlist.list_id所有用戶：

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)."' 

現在我想排除所有鏈接到當前組（GROUP_ID $）的participantlist.list_id的用戶，但我不能想出一個好辦法做到這一切在一個單一的查詢。我認爲解決的辦法將是某種形式的左連接/右或左/右外連接比較。

我的臨時工作，但非常昂貴的時間解決方案是這樣的：

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 

有什麼建議？

Answer 1

我會去的東西稍微簡單一些。

我覺得not in這裏是你的朋友。它應該讓你的代碼變得更容易閱讀和將最有可能讓MySQL的優化它多了幾分：

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."' 
       )