優化查詢仍需要多長時間

Question

如何優化此查詢？我曾嘗試使用LEFT JOIN條款，但仍至少需要3秒。

SELECT DISTINCT MBLNR 
FROM MKPF 
WHERE MANDT='368' 
    AND XBLNR = '0150525913' 
    AND MBLNR NOT IN (SELECT DISTINCT SMBLN FROM MSEG WHERE XBLNR_MKPF = '0150525913') 

使用LEFT JOIN後，仍需要3秒，得到的結果：

SELECT DISTINCT A.MBLNR 
FROM MKPF AS A 
LEFT JOIN MSEG AS B ON B.XBLNR_MKPF=A.XBLNR AND A.MBLNR <> B.SMBLN 
WHERE A.XBLNR = '0150525913' 

使用LEFT OUTER JOIN真的要花很多時間來返回行。

謝謝。

Answer 1

正確的左外連接第一個查詢的提法是：

SELECT DISTINCT A.MBLNR 
FROM MKPF A LEFT JOIN 
    MSEG B 
    ON B.SMBLN = A.MBLNR AND AND B.XBLNR_MKPF = '0150525913' 
WHERE A.XBLNR = '0150525913' and A.MANDT='368' and B.SMBLN is null; 

根據表的大小，3秒後可能是合理的。但是，您可以使用索引加速查詢。該查詢建議一些索引：MKPF(XBLNR, MANDT, MBLNR)和MSEG(XBLNR_MKPF, SMBLN)。

Answer 2

雖然直觀，「不在」是緩慢的。你爲什麼要使用不同的和left.If他們真的需要那麼其確定。或者你可以使用內部連接無明顯.Specially子查詢不

AND MBLNR NOT IN 
(SELECT DISTINCT SMBLN FROM MSEG WHERE XBLNR_MKPF = '0150525913') 

到

AND MBLNR IN 
(SELECT DISTINCT MBLNR 
FROM MKPF 
WHERE MANDT='368' 
AND XBLNR = '0150525913' 
except 
SELECT DISTINCT SMBLN 
FROM MSEG 
WHERE XBLNR_MKPF = '0150525913' 
) 

Answer 3

：所以，改變這種需要明確。

you can try not exists 
SELECT MBLNR 
FROM MKPF 
WHERE MANDT='368' 
    AND XBLNR = '0150525913' 
    AND NOT exists (SELECT SMBLN FROM MSEG WHERE XBLNR_MKPF = '0150525913')