SQL加入問題

Question

我有2個表格。

tblparents 
---------- 
parentid 
husbandid 
wifeid 

tblnode 
------- 
nodeid 
personid 
parentid 

我要的是一個SQL語句得到的parentid，丈夫/ wifeid和中行tblnode伯爵那裏的parentid的相等。在 'where子句' 未知列 't.parentid' -

我寫的代碼

SELECT t.parentid, t.spouseid, t.active, c.count FROM  
(SELECT parentid, wifeid spouseid from tblparents WHERE husbandid=1 
UNION 
SELECT parentid, husbandid spouseid from tblparents WHERE wifeid=1) t 
INNER JOIN 
(SELECT COUNT(*) count FROM tblnodes WHERE tblnodes.parentid=t.parentid) c; 

它給出了一個錯誤＃1054。

任何想法如何解決？

多謝，

Answer 1

出現語法錯誤。試試這個：

SELECT t.parentid, t.spouseid, t.active, c.count FROM  
(SELECT parentid, wifeid spouseid from tblparents WHERE husbandid=1 
UNION 
SELECT parentid, husbandid spouseid from tblparents WHERE wifeid=1) t 
INNER JOIN 
(SELECT parentid, COUNT(*) count 
FROM tblnodes GROUP BY parentid) c 
ON c.parentid=t.parentid) c ; 

但是，下面的查詢將有更好的表現：

SELECT t.parentid, t.wifeid spouseid, t.active, COUNT(t.parentid) CNT 
FROM tblparents t LEFT JOIN tblnode c 
    ON t.parentid = c.parentid 
GROUP BY t.parentid. t.wifeid, t.active 

Answer 2

試試這個：

SELECT t.parentid, t.spouseid, t.active, COALESCE(c.count, 0) AS count 
FROM (
    SELECT parentid, wifeid spouseid 
    FROM tblparents 
    WHERE husbandid = 1 

    UNION 

    SELECT parentid, husbandid spouseid 
    FROM tblparents 
    WHERE wifeid = 1 
) t 
LEFT JOIN (
    SELECT parentid, COUNT(*) count 
    FROM tblnodes 
    GROUP BY parentid 
) c 
    ON c.parentid = t.parentid 

Answer 3

如果我正確理解你的問題：

SELECT t.parentid, t.husbandid, t.wifeid, COUNT(*) 
LEFT JOIN tblnode n 
    ON n.parentid = t.parentid 
GROUP BY t.parentid. t.husbandid, t.wifeid 

編輯：這將返回的1最小計數雖然。

Answer 4

我想表的別名「T」是不是在最後陳述被認可。您需要爲聯合語句返回的集合指定一個別名，並在select count（*）語句中引用該別名。