如何提高這個sql查詢

Question

在這裏，我以小時和分鐘獲得了「ProcessTime」，但在幾秒鐘情況下，只有我檢查了相反的情況（見下面的代碼）

有什麼辦法改善嗎？

select convert(varchar(10),ScanDate,101) as [Date], tmb.WO, tc.WOCategory, count(IdSingle) QtyProd, tb.Brand, tm.Model, 
     (case when (DateDiff(mi, Min(convert(varchar(10),ScanDate,8)), Max(convert(varchar(10),ScanDate,8)))/60%24 > 0) then 
      convert(varchar(5), DateDiff(mi, Min(convert(varchar(10),ScanDate,8)), Max(convert(varchar(10),ScanDate,8)))/60%24) + 'h '    
       else 
      '' 
     end) + 
     (case when (DateDiff(mi, Min(convert(varchar(10),ScanDate,8)), Max(convert(varchar(10),ScanDate,8)))%60 > 0) then 
      convert(varchar(5), DateDiff(mi, Min(convert(varchar(10),ScanDate,8)), Max(convert(varchar(10),ScanDate,8)))%60) + 'm'    
       else 
      '' 
     end) +   
     (case when 
      (DateDiff(mi, Min(convert(varchar(10),ScanDate,8)), Max(convert(varchar(10),ScanDate,8)))/60%24 <= 0) and 
      (DateDiff(mi, Min(convert(varchar(10),ScanDate,8)), Max(convert(varchar(10),ScanDate,8)))%60 <= 0) then 
      '< 1 min' 
      else 
      '' 
     end) ProcessTime 

Answer 1

使用SQL Server 2005，您可以使用CTE來改進此查詢。
類似這樣的：

;WITH minmax AS 
(
    SELECT someKey, 
      DateDiff(mi, Min(convert(varchar(10),ScanDate,8)), Max(convert(varchar(10),ScanDate,8))) as mdiff 
    FROM tablename 
    GROUP BY fieldName 
) 
Select convert(varchar(10),ScanDate,101) as [Date], tmb.WO, tc.WOCategory, count(IdSingle) QtyProd, tb.Brand, tm.Model, 
     (case when (mdiff/60%24 > 0) then 
      convert(varchar(5), mdiff/60%24) + 'h '    
       else 
      '' 
     end) + 
     (case when (mdiff%60 > 0) then 
      convert(varchar(5), mdiff%60) + 'm'    
       else 
      '' 
     end) +   
     (case when 
      (DateDiff(mi, mdiff/60%24 <= 0) and (DateDiff(mi, mdiff%60 <= 0) then 
      '< 1 min' 
      else 
      '' 
     end) ProcessTime 
from tablename 
join minmax on tablename.somekey = minmax.somekey