Question

我有一张带有时间栏的表格。我正在尝试创建一个存储过程（SQL Server 2008）以获取每行的字符串，其中包含所有前一年的最后一个值和当前行值。例如，如果我有下表。

_________________
   time    value
_________________
mar-2009     1
_________________
may-2009     2
_________________
jan-2010     3
_________________
apr-2011     4
_________________
feb-2011     5
_________________
jan-2012     6
_________________

我想获得以下结果

____________________________________________________
   time    value          Result
____________________________________________________
mar-2009     1        "2009,1"
____________________________________________________
may-2009     2        "2009,2"
____________________________________________________
jan-2010     3        "2009,2,2010,3"
____________________________________________________
apr-2011     4        "2009,2,2010,3,2011,4"
____________________________________________________
feb-2011     5        "2009,2,2010,3,2011,5"
____________________________________________________
jan-2012     6        "2009,2,2010,3,2011,5,2012,6"
____________________________________________________

提前致谢。

Answer 1

您需要执行一个简单的SELECT来获取所有相关记录，然后遍历所有记录并将所需的输出连接成一个字符串（您可以在每个循环中输出累积的数据）。 http://www.techonthenet.com/sql_server/loops/for_loop.php

Answer 2

以下是示例，但出于性能目的，对原始表进行一些更改要好得多。

-- first we need to extract months/years to get comparable and sortable values
-- otherwise we can't select "all previous years" and "last value".
;with converted as (
    select
        time,
        right(time, 4) as year,
        datepart(m, '2000-' + left(time, 3) + '-01') as month,
        right(time, 4) + ',' + convert(varchar(16), value) as concatenated,
        value
    from
        YourTableName --TODO: Replace this with your table name
)
select
    time,
    value,
    -- using xml for string concatenation
    isnull((
        select
            prev.concatenated + ',' as 'text()'
        from
            converted as prev
        where
            prev.year < main.year
            and prev.month = (select max(month) from converted lookup where lookup.year = prev.year)
        for
            xml path('')
    ),'')
    + main.concatenated
from
    converted as main

SQL存储过程以获取所有前几年记录的连接字符串

2 个答案: