3

我有一个表，其中一个列（属性）包含名字、姓氏、帐号和与数据库中的事物相关的任何其他信息等信息。另一列 (attributeType) 包含一个数字，指示属性是什么，例如 1 可能是名字，2 姓氏和 3 帐号等。还有另一列 (enddate) 通过在那里有一个日期来指示记录是否是当前的。通常它会在当前设置为 9999 年，否则设置为过去的某个日期。描述同一事物的所有数据在另一列（实体）中也具有唯一值，因此实体列中具有相同编号的每条记录都将描述一个人。例如

entity  attribute  attributetype  enddate
------  ---------  -------------  --------
1       ben        1              9999-1-1
1       alt        2              9999-1-1
1       12345      3              9999-1-1
2       sam        1              9999-1-1
2       smith      2              9999-1-1
2       98765      3              1981-1-1

我想从上表中选择一个具有特定名字和姓氏的人，该名字将是当前的，但如果不是，则不输出帐号。假设该表名为 tblAccount，我对名称部分执行以下操作：

select ta1.attribute '1st Name', ta2.attribute 'last name'
from tblAccount ta1
inner join tblAccount ta2 on ta1.entity = ta2.entity
where ta1.attribute = 'sam' and ta2.attribute = 'smith'
      and ta1.attributetype = 1 and ta2. attributetype = 2
      and ta1.enddate > getdate() and ta2.enddate > getdate()

它按预期输出名字和姓氏，但是当我想包含帐号列时，我什么也没得到：

select ta1.attribute '1st Name', ta2.attribute 'last name', ta3.attribute 'account#'
from tblAccount ta1
inner join tblAccount ta2 on ta1.entity = ta2.entity
left join tblAccount ta3 on ta1.entity = ta3.entity
where ta1.attribute = 'sam' and ta2.attribute = 'smith'
      and ta1.attributetype = 1 and ta2. attributetype = 2
      and ta1.enddate > getdate() and ta2.enddate > getdate()
      and ta3.attributetype = 3 and ta3.enddate > getdate()

我想看到的是在上述情况下，在 account# 列中没有任何内容输出的名字和姓氏，但它不是最新的。我做错了什么，如何更正此查询？

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2 回答 2

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You have to move the date comparison to the join condition:

select ta1.attribute '1st Name'
    , ta2.attribute 'last name'
    , ta3.attribute 'account#'
from tblAccount ta1
inner join tblAccount ta2 
    on ta1.entity = ta2.entity
     and ta1.attributetype = 1 and ta2. attributetype = 2
     and ta1.enddate > getdate() and ta2.enddate > getdate()
left join tblAccount ta3 on ta1.entity = ta3.entity
      and ta3.attributetype = 3 and ta3.enddate > getdate()
where ta1.attribute = 'sam' and ta2.attribute = 'smith'

When it's in the where clause it's comparing getdate() to NULL if there is no account, which returns NULL. So no record.

EDIT:

In response to the valid concern about multiple valid records, and to make the code a little more maintenance freindly:

DECLARE @FNAME VARCHAR(50) = 'sam'
    , @LNAME VARCHAR(50) = 'smith'
    , @now DATETIME2(7) = GETDATE();

SELECT 
    name.[1st Name]
    , name.[last name]
    , name.entity
    , 
        (
            select 
                top 1 
                ta3.attribute
            FROM tblAccount ta3 
            WHERE 
                ta3.entity = name.entity
                and 
                ta3.attributetype = 3 
                and 
                ta3.enddate > @now
            ORDER BY 
                ta3.enddate 
        )
FROM 
    (        
        select 
            ta1.attribute '1st Name'
            , ta2.attribute 'last name'
            , ta.entity
            , ROW_NUMBER()
                OVER(
                    PARTITION BY 
                        ta1.entity
                    ORDER BY 
                        ta1.enddate
                    ) r
        from 
            tblAccount ta1
        inner join tblAccount ta2 
            on 
            ta1.entity = ta2.entity
            and 
            ta2. attributetype = 2
            and 
            ta2.enddate > @now
            and 
            ta2.attribute = @LNAME
        where 
            ta1.attributetype = 1 
            and 
            ta1.attribute = @fname 
            and 
            ta1.enddate > @now
    ) name
WHERE    
    NAME.r = 1

;

This code works around the implied assumptions of one entity per first/last name and exactly one enddate after the execution time. The variables are a little more stored proc friendly, and allow you to change the "as of" date. And if you're stuck with EAV, you will likely want stored procs. I'm taking the first record ending after the date in question, on the assumption that any later record(s) should only be valid after that one expires. Maybe it's overkill, since it's beyond the scope of the OP's question but it's a valid point.

I say "stuck with EAV". While EAV isn't always bad; neither is shooting someone in the back. In either case, you'd better have solid justification if you expect to get it past a jury. In a NoSQL storage pattern it's fine, but EAV is usually a poor implementation pattern for the RDBMS paradigm.

Though from the OP's later comment, it looks like he's hit on one of the better reasons.

于 2013-03-07T15:29:02.010 回答
1

在这个模型中，每个属性实际上是一个不同的实体，但它们都在同一个物理表中共享相同的存储（为什么？）。这产生：

with data as (
   select entity = 1, attribute = 'ben',   attributeType=1, enddate = convert(datetime,'99990101') union all
   select entity = 1, attribute = 'alt',   attributeType=2, enddate = convert(datetime,'99990101') union all
   select entity = 1, attribute = '12345', attributeType=3, enddate = convert(datetime,'99990101') union all
   select entity = 2, attribute = 'sam',   attributeType=1, enddate = convert(datetime,'99990101') union all
   select entity = 2, attribute = 'smith', attributeType=2, enddate = convert(datetime,'99990101') union all
   select entity = 2, attribute = '67890', attributeType=3, enddate = convert(datetime,'99990101') union all
   select entity = 2, attribute = '68790', attributeType=3, enddate = convert(datetime,'20130331') union all
   select entity = 2, attribute = '876', attributeType=3, enddate = convert(datetime,'19810101') 
) 
select top 1
    FirstName, LastName, AccountNum
from (
  select top 1 
    a1.entity, FirstName, LastName
  from (
    select entity, enddate, attribute as FirstName
    from data d 
    where d.enddate >= getdate()
      and attributeType = 1
  ) a1
  join (
    select entity, enddate, attribute as LastName
    from data 
    where enddate >= getdate()
      and attributeType = 2
  ) a2 on a1.entity = a2.entity
     and a1.enddate = a2.enddate
  where FirstName = 'sam' and LastName = 'smith'
    and a1.enddate >= getdate() and a2.enddate >= getdate()
  order by a1.enddate
) E
left join (
  select entity, enddate, attribute as AccountNum
  from data 
  where enddate >= getdate()
    and attributeType = 3
) a3 on a3.entity = E.entity
order by a3.enddate

返回：

FirstName LastName AccountNum
--------- -------- ----------
sam       smith    68790

请注意，至少对于会计部门来说，在一个月的安静时间输入未来的交易是很常见的，特别是如果这些交易将在一个月的繁忙时间（即月末）生效。年度交易也是如此。不应该假设只有一条记录可以存在到期 > getdate()。

于 2013-03-07T15:45:44.137 回答