即興SQL查詢

Question

我有下面的SQL，需要1或2秒返回結果。我在光標內調用這個SQL 500次以上。我正試圖重寫這個查詢。

SELECT Sum(CASE 
       WHEN UpdatedAdjustedOT IS NOT NULL 
        AND UpdatedAdjustedOT != '' 
        AND UpdatedAdjustedOT != '0' 
        THEN CONVERT(DECIMAL(18, 2), UpdatedAdjustedOT) 
       ELSE 0 
       END) AS OTHours 
    FROM tbl_OTAuthorization 
    WHERE EmployeeCodeFK = @EmployeeCode 
     AND month(OTDate) = Month(@FromDate) 
     AND year(OTDate) = Year(@FromDate) 

請建議我以更好的方式

Answer 1

首先，重新寫WHERE條款看起來像這樣：

SELECT . . . 
FROM tbl_OTAuthorization 
WHERE EmployeeCodeFK = @EmployeeCode AND 
     OTDate >= DATEADD(day, 1 - DAY(@FromDate), @FromDate) AND 
     OTDate < DATEADD(month, 1, DATEADD(@FromDate, 1 - DAY(@FromDate), @FromDate)); 

其次，創建表適當指數：

CREATE INDEX tbl_OTAuthorization_2 ON tbl_OTAuthorization(EmployeeCodeFK, OTDate, UpdatedAdjustedOT); 

第三，返回並修復您的代碼，以防止員工和日期循環。您應該能夠在單個查詢中處理邏輯。通常，如果要優化使用數據庫的性能，請避免使用遊標。

Answer 2

不要在函數結果中過濾如何重新寫這個查詢。找到一種方法來取代這個：

AND month(OTDate) = Month(@FromDate) 
AND year(OTDate) = Year(@FromDate) 

到這樣的事情：

and OTDate >= the first day of the month for @FromDate 
and OTDate < the first day of the month following @FromDate 

Answer 3

試試這個：

SELECT Sum(CONVERT(DECIMAL(18, 2), ISNULL(NULLIF(UpdatedAdjustedOT, ''), 0))) as OTHours 
    FROM tbl_OTAuthorization 
    WHERE EmployeeCodeFK = @EmployeeCode 
     AND month(OTDate) = Month(@FromDate) 
     AND year(OTDate) = Year(@FromDate) 

Answer 4

WHERE EmployeeCodeFK = @EmployeeCode 
    AND OTDate >= DATEADD(MONTH, DATEDIFF(MONTH, 0, @FromDate), 0) 
    AND OTDate < DATEADD(MONTH, 1, DATEADD(MONTH, DATEDIFF(MONTH, 0, @FromDate), 0))