oracle 左连接四表关联查询示例

 

1.情景展示

　　查询指定时间段内的某卡的每天的注册量

2.原因分析

　　使用group by按天进行分组查询，并将查询结果看做一张表；

　　connect by递归查询出指定时间段所横跨的日期作为主表，注册量作为辅表，与主表日期进行关联查询 

3.解决方案

SELECT NVL(APP_ZS, 0) ONLINE_FORMAL, --''转0
       NVL(APP_LS, 0) ONLINE_INFORMAL,
       NVL(JG_ZS, 0) OFFLINE_FORMAL,
       NVL(JG_LS, 0) OFFLINE_INFORMAL,
       D.REGDATE REGTIME
  FROM (SELECT COUNT(1) APP_ZS, /*线上正式卡注册量*/
               TO_CHAR(V.REGTIME, 'YYYY-MM-DD') REGDATE
          FROM VIRTUAL_CARD V, APP_ACCESS A
         WHERE V.IDENTIFIER = A.ID
         GROUP BY TO_CHAR(V.REGTIME, 'YYYY-MM-DD')) ONLINE_FORMAL_CARD_REGIST,
       (SELECT COUNT(1) APP_LS, /*线上临时卡注册量*/
               TO_CHAR(V.REGTIME, 'YYYY-MM-DD') REGDATE
          FROM VIRTUAL_CARD_INTERIM V, APP_ACCESS A
         WHERE V.IDENTIFIER = A.ID
         GROUP BY TO_CHAR(V.REGTIME, 'YYYY-MM-DD')) ONLINE_INFORMAL_CARD_REGIST,
       (SELECT COUNT(1) JG_ZS, /*线下正式卡注册量*/
               TO_CHAR(V.REGTIME, 'YYYY-MM-DD') REGDATE
          FROM VIRTUAL_CARD V, ORG_ACCESS O
         WHERE V.IDENTIFIER = O.ID
         GROUP BY TO_CHAR(V.REGTIME, 'YYYY-MM-DD')) OFFLINE_FORMAL_CARD_REGIST,
       (SELECT COUNT(1) JG_LS, /*线下临时卡注册量*/
               TO_CHAR(V.REGTIME, 'YYYY-MM-DD') REGDATE
          FROM VIRTUAL_CARD_INTERIM V, ORG_ACCESS O
         WHERE V.IDENTIFIER = O.ID
         GROUP BY TO_CHAR(V.REGTIME, 'YYYY-MM-DD')) OFFLINE_INFORMAL_CARD_REGIST,
       /*左连接（以天为主表）*/
       (SELECT TO_CHAR(TO_DATE('2020-06-01', 'YYYY-MM-DD') + ROWNUM - 1,
                       'YYYY-MM-DD') AS REGDATE
          FROM DUAL
        CONNECT BY ROWNUM <=
                   TRUNC(TO_DATE('2020-06-17', 'YYYY-MM-DD') -
                         TO_DATE('2020-06-01', 'YYYY-MM-DD')) + 1) D
 WHERE D.REGDATE = ONLINE_FORMAL_CARD_REGIST.REGDATE(+)
   AND D.REGDATE = ONLINE_INFORMAL_CARD_REGIST.REGDATE(+)
   AND D.REGDATE = OFFLINE_FORMAL_CARD_REGIST.REGDATE(+)
   AND D.REGDATE = OFFLINE_INFORMAL_CARD_REGIST.REGDATE(+)
 ORDER BY D.REGDATE;

写在最后

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