Question

我在sqlite中使用了sql查询，实际上是3个SELECT语句的UNION。

我想简化它。有人能帮助我吗？

Select *, "A" as Status
  FROM (SELECT ADM_ID,
               Dte_Implantation,
               Dte_modif,
               SUP_EMETTEUR_052016.EMR_ID         as 'EMR_ID',
               SUP_EMETTEUR_052016.STA_NM_ANFR    as 'STA_NM_ANFR',
               SUP_EMETTEUR_052016.EMR_LB_SYSTEME as 'EMR_LB_SYSTEME'
          FROM SUP_STATION_052016
          left outer join SUP_EMETTEUR_052016
            ON SUP_STATION_052016.STA_NM_ANFR =
               SUP_EMETTEUR_052016.STA_NM_ANFR
         WHERE Dte_Implantation >
               (SELECT MAX(Dte_Implantation) FROM SUP_STATION_042016)
           AND (ADM_ID = 6 or ADM_ID = 23 or ADM_ID = 137 or
               ADM_ID = 240))
UNION ALL
select *, "A" as Status
  FROM (SELECT ADM_ID,
               Dte_Implantation,
               Dte_modif,
               SUP_EMETTEUR_052016.EMR_ID         as 'EMR_ID',
               SUP_EMETTEUR_052016.STA_NM_ANFR    as 'STA_NM_ANFR',
               SUP_EMETTEUR_052016.EMR_LB_SYSTEME as 'EMR_LB_SYSTEME'
          FROM SUP_STATION_052016
          left outer join SUP_EMETTEUR_052016
            ON SUP_STATION_052016.STA_NM_ANFR =
               SUP_EMETTEUR_052016.STA_NM_ANFR
         WHERE Dte_modif >
               (SELECT MAX(Dte_Implantation) FROM SUP_STATION_042016)
           AND (ADM_ID = 6 or ADM_ID = 23 or ADM_ID = 137 or
               ADM_ID = 240) EXCEPT
          SELECT ADM_ID,
                 Dte_Implantation,
                 Dte_modif,
                 SUP_EMETTEUR_042016.EMR_ID         as 'EMR_ID',
                 SUP_EMETTEUR_042016.STA_NM_ANFR    as 'STA_NM_ANFR',
                 SUP_EMETTEUR_042016.EMR_LB_SYSTEME as 'EMR_LB_SYSTEME'
                  FROM SUP_STATION_052016
                  left outer join SUP_EMETTEUR_042016
                    ON SUP_STATION_052016.STA_NM_ANFR =
                       SUP_EMETTEUR_042016.STA_NM_ANFR
                 WHERE Dte_modif >
                       (SELECT MAX(Dte_Implantation)
                          FROM SUP_STATION_042016)
                   AND (ADM_ID = 6 or ADM_ID = 23 or ADM_ID = 137 or
                       ADM_ID = 240)
        )
UNION ALL
select *, "S" as Status
  FROM (SELECT ADM_ID,
               Dte_Implantation,
               Dte_modif,
               SUP_EMETTEUR_042016.EMR_ID         as 'EMR_ID',
               SUP_EMETTEUR_042016.STA_NM_ANFR    as 'STA_NM_ANFR',
               SUP_EMETTEUR_042016.EMR_LB_SYSTEME as 'EMR_LB_SYSTEME'
          FROM SUP_STATION_052016
          left outer join SUP_EMETTEUR_042016
            ON SUP_STATION_052016.STA_NM_ANFR =
               SUP_EMETTEUR_042016.STA_NM_ANFR
         WHERE Dte_modif >
               (SELECT MAX(Dte_Implantation) FROM SUP_STATION_042016)
           AND (ADM_ID = 6 or ADM_ID = 23 or ADM_ID = 137 or
               ADM_ID = 240) EXCEPT
          SELECT ADM_ID,
                 Dte_Implantation,
                 Dte_modif,
                 SUP_EMETTEUR_052016.EMR_ID         as 'EMR_ID',
                 SUP_EMETTEUR_052016.STA_NM_ANFR    as 'STA_NM_ANFR',
                 SUP_EMETTEUR_052016.EMR_LB_SYSTEME as 'EMR_LB_SYSTEME'
                  FROM SUP_STATION_052016
                  left outer join SUP_EMETTEUR_052016
                    ON SUP_STATION_052016.STA_NM_ANFR =
                       SUP_EMETTEUR_052016.STA_NM_ANFR
                 WHERE Dte_modif >
                       (SELECT MAX(Dte_Implantation)
                          FROM SUP_STATION_042016)
                   AND (ADM_ID = 6 or ADM_ID = 23 or ADM_ID = 137 or
                       ADM_ID = 240)
        )

Answer 1

在没有实际重写查询的情况下帮助简化有点困难，但我会尝试给出可能有帮助的一般指示。

1）您可以使用

之类的东西统一第一个和第二个子查询

WHERE (ADM_ID = 6 or ADM_ID = 23 or ADM_ID = 137 or ADM_ID = 240)
  AND (Dte_Implantation > (select max ...)
   OR (Dte_modif > (select max ...)
  AND NOT EXISTS (SELECT 1 FROM SUP_STATION_052016 ...)))

当然使用WHERE NOT EXISTS或LEFT JOIN ... WHERE somefield IS NULL取决于您的DBMS优化程序，该选择取决于您

2）除此之外，您还可以通过将LEFT OUTER JOIN SUP_EMETTEUR_042016 ...与

组合来统一第三个查询

CASE
  WHEN OneTable.MandatoryField IS NULL AND AnotherTable.MandatoryField IS NOT NULL THEN 'S'
  WHEN OneTable.MandatoryField IS NOT NULL AND AnotherTable.MandatoryField IS NULL THEN 'A'
  WHEN ...
END AS Status

3）此外，您可以尝试通过使用表别名来使查询更具可读性（仅用SUP_EMETTEUR_042016.EMR_LB_SYSTEME等替换SE4.EMR_LB_SYSTEME之类的长项。可能会将长条件ADM_ID = 6 or ADM_ID = 23 or ADM_ID = 137 or ADM_ID = 240替换为更短的ADM_ID IN (6, 23, 137, 240)也会给出一个镜头。

4）为了提高可读性，您可以尝试使用公用表表达式来消除多用(SELECT MAX(Dte_Implantation) FROM SUP_STATION_042016)

WITH max_di AS (SELECT MAX(Dte_Implantation) AS val FROM SUP_STATION_042016)
...(your select here)
FROM max_di
    INNER JOIN SUP_STATION_052016 SS5
            ON (..conditions here..
           AND SS5.Dte_Implantation > max_di.val)

希望这件事能以某种方式帮助你。祝你重构好运=）

简化SQL请求

1 个答案: