SQL加入訂單結果的日期和PK

Question

好的，我主要處理相當簡單的SQL，事實上，我目前的問題似乎應該很簡單，但我一直沒有能夠提出正確的搜索條件來尋找解決方案。我以一對多的關係加入兩張桌子。我想按第二張表中的日期字段進行排序，同時按PK對結果進行分組。

MAIN 
-- 
MAINID, ACTION, DIVISION 
000001, HRREC, I 
000002, AUDIT, IV 
000003, TRAVEL, II 

SECONDARY 
-- 
MAINID, AUTHUSER, LOGINDATE, COMMENTS 
000002, Fred,  01/02/2012, Needs work 
000001, Smitty, 01/05/2012, making brisk progress 
000003, Fred,  03/10/2012, blah blah 
000002, Jimmy, 02/15/2011, something 
000001, Bill,  01/01/2012, neener neener 
000002, Saul,  12/13/2011, no action 

DESIRED OUTPUT 
-- 
MAINID, ACTION, DIVISION, AUTHUSER, LOGINDATE, COMMENTS 
000003, TRAVEL, II,  Fred,  03/10/2012, blah blah 
000001, HRREC, I,  Smitty, 01/05/2012, making brisk progress 
000001, HRREC, I,  Bill,  01/01/2012, neener neener 
000002, AUDIT, IV,  Fred,  01/02/2012, Needs work 
000002, AUDIT, IV,  Saul,  12/13/2011, no action 
000002, AUDIT, IV,  Jimmy, 02/15/2011, something 

The basic join I'd like to order 
-- 
SELECT MAIN.MAINID,MAIN.DIVISION,MAIN.ACTION,SECONDARY.AUTHUSER,SECONDARY.LOGINDATE,SECONDARY.COMMENTS 
FROM MAIN 
LEFT JOIN SECONDARY ON MAIN.MAINID=SECONDARY.MAINID; 

謝謝！

Answer 1

如果您想通過LOGINDATE訂購內通過MAINID與MAX（LOGINDATE）排序組由組你sholud做到這一點：

SELECT 
    M.MAINID, 
    M.DIVISION, 
    M.ACTION, 
    S.AUTHUSER, 
    S.LOGINDATE, 
    S.COMMENTS 
FROM MAIN M LEFT OUTER JOIN (
     SELECT 
      MAINID, 
      MAX(LOGINDATE) MAXDATE 
     FROM SECONDARY 
     GROUP BY 
      MAINID 
    ) Q 
      ON M.MAINID=Q.MAINID 
     LEFT JOIN SECONDARY S 
      ON M.MAINID=S.MAINID 
ORDER BY 
    MAXDATE, LOGINDATE;