Mysql查詢組合

Question

我有一個查詢，它由3個表a，b，c組合而成，這里的問題是表c存在於2個數據庫D1和D2中，所以我必須從兩個數據庫中獲取表c的記錄。表a和b僅來自數據庫D1，

查詢是：

$strQuery="SELECT a.id, b.lastname, school " ."FROM D1.a,D1.b" .
    " WHERE a.idint = (select c_idint from D1.c where Cid IN(10) 
UNION select c_idint from D2.c where Cid IN(10) order by c_idint)
 AND a.idint = b.idb";

問題是字段“學校”來自表c，如果我從查詢中避免字段“學校”它工作正常，但我也必須獲取字段'學校'，我如何修改查詢。 謝謝：）

Answer 1

你需要的是別名 ，

$strQuery="SELECT a.id, b.lastname, D2.c.school as school1,D1.c.school as school2 " ."FROM D1.a,D1.b,D1.c,d2.c" .
          " WHERE a.idint = (select c_idint from D1.c where Cid IN(10) 
          UNION select c_idint from D2.c where Cid IN(10) order by c_idint)
          AND a.idint = b.idb";

Answer 2

嘗試這樣： -

$strQuery="SELECT a.id, b.lastname, c.school " ."FROM D1.a,D1.b,D1.c" .
 " WHERE a.idint = (select c_idint from D1.c where Cid IN(10) 
UNION select c_idint,school from D2.c where Cid IN(10) order by c_idint)
AND a.idint = b.idb";

Answer 3

嘗試這個：

$strQuery="SELECT a.id, b.lastname, c.school as dSchool, '' as ddSchool " ."FROM D1.a,D1.b, D1.c" .
    " WHERE a.idint = c.idint AND c.Cid IN (10)
 AND a.idint = b.idb

UNION 

SELECT a.id, b.lastname, '' as dSchool, c.school as ddSchool " ."FROM D1.a,D1.b, D2.c" .
    " WHERE a.idint = c.idint AND c.Cid IN (10)
 AND a.idint = b.idb
";