選擇並計算表關係？

Question

我有03桌有關係

jos_session 
+userid 

jos_gj_user 
    +id_user 
    +id_group 

jos_gj_jb 
    +group_id 
    +category_id 

我是要計算用戶在表jos_session基礎上CATEGORY_ID表jos_gj_jb

這是我想

SELECT COUNT(s.userid) 
FROM jos_session s 
WHERE s.user.id IN (SELECT id_user 
        FROM jos_gj_user 
        WHERE id_group(SELECT group_id FROM jos_gj_jb WHERE category_id= .$variable.)) 

怎麼算user_id爲category_id？

Answer 1

雖然我沒有絕對的把握，如果我明白你的問題，這裏是我的建議：

SELECT COUNT(DINSTINCT id_user) 
FROM jos_gj_user INNER JOIN jos_gj_jb ON id_group = group_id 
WHERE category_id= $variable 

這個查詢將返回不同用戶的數量是關係到通過引用的類別之一的成員或我的團值爲$variable。

Answer 2

SELECT COUNT(DINSTINCT id_user) 
FROM jos_session INNER JOIN jos_gj_user ON id_user = userid INNER JOIN jos_gj_group ON id_group = group_id 
WHERE category_id= $variable GROUP BY category_id