MySQL查詢最新的日期

Question

我運行此查詢

SELECT sh.*, 
     u.initials AS initals 
    FROM database1.table1 AS sh 
    JOIN database2.user AS u ON u.userID = sh.userid 
WHERE id = 123456 
    AND dts = (SELECT MAX(dts) from database1.table1) 
ORDER BY sort_by, category 

在表1我有這樣

dts       status     category   sort_by 
2010-04-29 12:20:27  Civil Engineers   Occupation 1 
2010-04-28 12:20:27  Civil Engineers   Occupation 1 
2010-04-28 12:20:54 Married    Marital Status 2  2010-04-28 12:21:15 Smoker    Tobbaco 3 
2010-04-27 12:20:27  Civil Engineers   Occupation 1 
2010-04-27 12:20:54 Married    Marital Status 2  2010-04-27 12:21:15 Smoker    Tobbaco 3 
2010-04-26 12:20:27  Civil Engineers   Occupation 1 
2010-04-26 12:20:54 Married    Marital Status 2  2010-04-26 12:21:15 Smoker    Tobbaco 3 

記錄如果你看看我的數據，我選擇按類別的最新條目和sort_id。但在某些情況下，如29日（2010-04-29 12:20:27）我只有一條記錄。因此，在這種情況下，我想顯示最新的職業，然後顯示其他職位（最新）。但目前它只顯示一行。

Answer 1

試圖爲最好你有什麼猜測，您的查詢將不得不調整無論如何，像

SELECT 
     sh.dts, 
     cast(if(preAgg1.totalPerCatSort = 1, sh.status, ' ') as char(20)) 
      as SingleStatus, 
     sh.category, 
     sh.sort_by, 
     u.initials AS initals 
    FROM 
     database1.table1 AS sh, 
     database2.user AS u, 
     (select 
       t1.category, 
       t1.sort_by, 
       max(dts) maxdts, 
       count(*) totalPerCatSort 
      from 
       database1 t1 
      group by 
       t1.category, 
       t1.sort_by) preAgg1 
    WHERE 
     sh.userid = u.userID 
    and sh.sort_by = preAgg1.sort_by 
    and sh.category = preAgg1.category 
    and sh.dts = preAgg1.maxdts 
    and id = 123456 ?? Should this actually be the UserID column ?? 
    ORDER BY 
    sort_by, 
    category 

你可能要應用「ID = 123456」到「preAgg1」子選擇，但不能確定該列/表適用於哪個ID，否則，您可能有其他「用戶」的日期條目，而對於您正在尋找的一個候選人，則可能不同。

每你獲得的所有記錄的關注，我只想刪除您「和ID = 123456」限定符和所有要善於