Question

我理解如何使用左连接返回空行，但这对我不起作用。有没有人对如何返回与连接无关但与where相关的空白行有一些建议。我希望为每个成员拾取最近的行，这适用于所有具有结束日期行的活动成员，但是在他们的TERMDATE＆lt;＆gt;为空我需要返回一个空行或拾取最近一行。任何和所有的帮助非常感谢。感谢

SELECT MCSERVICEAUTHORIZATIONS.AUTHNUMBER, CLIENTS.SUBSCRIBERID, MCSERVICEAUTHORIZATIONS.AUTHTYPE, MCSERVICEAUTHORIZATIONS.AUTHSTATUS,  GRDSHSCLIENTINSURANCE.LOB, GRDSHSCLIENTINSURANCE.ENROLLMENTDATE, GRDSHSCLIENTINSURANCE.TERMDATE
FROM GRDSHSCLIENTINSURANCE 
INNER JOIN CLIENTS 
ON GRDSHSCLIENTINSURANCE.PARENTID = CLIENTS.ID 
INNER JOIN MCSERVICEAUTHORIZATIONS 
ON CLIENTS.ID = MCSERVICEAUTHORIZATIONS.PARENTID
WHERE (MCSERVICEAUTHORIZATIONS.AUTHTYPE = 1234) 
AND (GRDSHSCLIENTINSURANCE.TERMDATE IS NULL)

Answer 1

大多数数据库都支持可以真正帮助进行此类查询的窗口/分析函数。特别是，您可以使用dense_rank()函数枚举每组GRDSHSCLIENTINSURANCE条记录的行，因此首先是NULL终止日期，然后是降序排列的终止日期。你只需要选择第一个：

SELECT sa.AUTHNUMBER, ci.SUBSCRIBERID, sa.AUTHTYPE, sa.AUTHSTATUS,
       ci.LOB, ci.ENROLLMENTDATE, ci.TERMDATE
FROM (select ci.*,
             dense_rank() over (partition by parentid
                                order by (case when termdate is null then 0 else 1 end),
                                         termdate desc
                               ) as seqnum
      from GRDSHSCLIENTINSURANCE ci
     ) ci INNER JOIN
     CLIENTS c
     ON ci.PARENTID = c.ID INNER JOIN
     MCSERVICEAUTHORIZATIONS sa
     ON c.ID = sa.PARENTID
WHERE sa.AUTHTYPE = 1234 AND
      ci.seqnum = 1;

请注意，此查询使用dense_rank()。这允许返回多行，即使有两行都具有NULL值。

此外，我添加了表别名以使查询更具可读性。

查询返回空白行

1 个答案: