Question

您能否帮我优化此查询：

select distinct PUBLSEQ from PUBLCOVER P
          WHERE EXISTS
          ( SELECT * FROM PUBLCOVER A, COVERAREA B, PRODCODEDICT C
            WHERE A.PUBLSEQ = P.PUBLSEQ
            AND A.COVER_STATUS = 'Y'
            AND A.COVAREA = B.COVAREA
            AND B.COVAREA_PRODCODE IS NOT NULL
            AND B.COVAREA_PRODCODE = C.PRODCODE
            AND C.STATUS = 'A'
            AND A.COVAREA = 1823
            )
          AND NOT EXISTS
          ( SELECT * FROM PUBLCOVER A, COVERAREA B, PRODCODEDICT C
            WHERE A.PUBLSEQ = P.PUBLSEQ
            AND A.COVER_STATUS = 'Y'
            AND A.COVAREA = B.COVAREA
            AND B.COVAREA_PRODCODE IS NOT NULL
            AND B.COVAREA_PRODCODE = C.PRODCODE
            AND C.STATUS = 'A'
            AND A.COVAREA NOT IN (1823, 34)
            )

我想逃离EXISTS或NOT EXISTS，只留下一个。

Answer 1

您应该能够消除这两者并在HAVING子句中使用条件聚合，例如：

SELECT A.PUBLSEQ
FROM PUBLCOVER A
    JOIN  COVERAREA B
    ON A.COVAREA = B.COVAREA
    JOIN  PRODCODEDICT C
    ON B.COVAREA_PRODCODE = C.PRODCODE
WHERE A.COVER_STATUS = 'Y'
    AND B.COVAREA_PRODCODE IS NOT NULL
    AND C.STATUS = 'A'
GROUP BY A.PUBLSEQ
HAVING MAX(CASE WHEN A.COVAREA NOT IN (1823, 34) THEN 1 ELSE 0 END) = 0
  AND  MAX(CASE WHEN A.COVAREA = 1823 THEN 1 ELSE 0 END) = 1

可能需要将WHERE条件移至条件聚合，如下所示：

SELECT A.PUBLSEQ
FROM PUBLCOVER A
    JOIN  COVERAREA B
    ON A.COVAREA = B.COVAREA
    JOIN  PRODCODEDICT C
    ON B.COVAREA_PRODCODE = C.PRODCODE
GROUP BY A.PUBLSEQ
HAVING MAX(CASE WHEN A.COVAREA NOT IN (1823, 34)
                 AND A.COVER_STATUS = 'Y'
                 AND B.COVAREA_PRODCODE IS NOT NULL
                 AND C.STATUS = 'A' THEN 1 
                ELSE 0 
           END) = 0
  AND  MAX(CASE WHEN A.COVAREA = 1823  AND A.COVER_STATUS = 'Y'
                 AND B.COVAREA_PRODCODE IS NOT NULL
                 AND C.STATUS = 'A' 
                THEN 1 ELSE 0 
            END) = 1

在您的问题中，您没有提供足够的信息来确切了解您的需求，但上述两条建议已接近。

你能帮我优化一下sql查询db2吗？

1 个答案: