Question

我有一个查询，我总是希望返回10条记录：

set rowcount 10
select row_number() over(order by count(*) desc) row_num
    ,hist_report_id
    ,max(rpt_report_name) report_name
from utility.dbo.tbl_report_history
join utility.dbo.tbl_report_definitions
    on hist_report_id = rpt_report_id
where hist_user_id = 1038
group by hist_report_id

如果我有10个或更多记录，哪个工作正常。问题是当记录少于10条时，我仍然需要在report_id和report_name字段中返回带有空值的rownumber字段。

如果只返回了7条记录，结果应如下所示：

row_num report_id report_name
1       id1       name1
2       id2       name2
3       id3       name3
4       id4       name4
5       id5       name5
6       id6       name6
7       id7       name7
8       null      null
9       null      null
10      null      null

有什么建议吗？

我正在使用SQL Server 2008

Answer 1

count()永远不会返回小于零...所以只需在计数列中通过union附加10个带有-1的虚拟行

此外，请勿使用SET ROWCOUNT，因为它会影响中间结果

SELECT TOP 10
   row_number() over(order by TheCount desc) AS row_num,
   hist_report_id,
   report_name
FROM
    (
    select 
        ,count(*) AS TheCount
        ,hist_report_id
        ,max(rpt_report_name) AS report_name
    from 
       utility.dbo.tbl_report_history
       join 
       utility.dbo.tbl_report_definitions on hist_report_id = rpt_report_id
    where hist_user_id = 1038
    group by hist_report_id
    UNION ALL
    SELECT TOP 10
         -1, NULL, NULL
    FROM sys.columns
    ) T

Answer 2

with
/* Create 10 dummy rows using recursion */
RowSequence as (
    select 0 Idx
    union all
    select RowSequence.Idx+1 Idx from RowSequence where RowSequence.Idx+1<10
    ),
/* Your Query */
YourQuery as(
    select row_number() over(order by count(*) desc) row_num
        ,hist_report_id
        ,max(rpt_report_name) report_name
    from utility.dbo.tbl_report_history
    join utility.dbo.tbl_report_definitions
        on hist_report_id = rpt_report_id
    where hist_user_id = 1038
    group by hist_report_id
    )
/* Now all together */
select top 10 * from (
    select * from YourQuery
    union all
    select null, null, null from RowSequence
    ) a
/* To avoid the recursion maximum level 100 */
option (maxrecursion 0)

Answer 3

我记得最简单的方式：

Insert select result

#temptable

While count(*) < 10 insert行into #temptable

Answer 4

您可以考虑使用TVF为您返回一组您可以加入的数字：

CREATE FUNCTION SetOfValues (@beginningAt int, @endingAt int, @step int = 1)
RETURNS 
    @result TABLE (value int )
AS BEGIN
    declare @counter int set @counter = @beginningAt
    while(@counter<=@endingAt)
    begin
        insert into @result values(@counter)
        set @counter = @counter + @step
    end 
RETURN 
END
GO

-- USAGE
with cte as (
    select row_number() over (order by hist_report_Id) as row_num,
    hist_report_Id, report_name
    from tbl_report_history join tbl_report_definitions on hist_report_Id = rpt_reportId)
select value, hist_reportId, report_name 
from dbo.SetOfValues(1,10,1) as t on t.value = cte.row_num

始终返回指定数量的记录Sql Server

4 个答案: