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我有一个格式如下的表（我使用的是 MS SQL Server 2008）：

car_id | trace
1        1300275738;57.72588;11.84981;0.00026388888888888886;1300275793;57.72596;11.8529;0.001055...

跟踪值是一个以分号作为分隔符的 csv 字符串。跟踪字符串中的值分为四组和四组，如下所示（没有换行符除外）：

1300275738;57.72588;11.84981;0.00026388888888888886;
1300275793;57.72596;11.8529;0.0010555555555555555;
1300275785;57.72645;11.85242;0.007416666666666665;
1300275780;57.72645;11.85242;0.0010138888888888888;

我想要做的是在插入时创建一个触发器，该触发器根据四个组中的第一个值对跟踪字符串进行排序。所以上面的结果会变成

1300275738;57.72588;11.84981;0.00026388888888888886;1300275780;57.72645;11.85242;0.0010138888888888888;1300275785;57.72645;11.85242;0.007416666666666665;1300275793;57.72596;11.8529;0.0010555555555555555;

我试图做的是将值拆分为临时表中的单独行，如下所示：

USE tempdb
GO

checkpoint
dbcc dropcleanbuffers
dbcc freeproccache
GO

--declare a variable and populate it with a comma separated string
DECLARE @SQLString VARCHAR(MAX)
SET @SQLString = (SELECT trace FROM mypev_trips.dbo.trips)

--append a comma to the string to get correct results with empty strings or strings with a single value (no commas)
SET @SQLString = @SQLString + ';';

DECLARE @X XML
SET @X = CAST('<A>' + REPLACE(@SQLString, ';', '</A><A>') + '</A>' AS XML)

SELECT t.value('.', 'nvarchar(20)')
FROM @x.nodes('/A') as x(t)

这给出了以下结果：

(No column name)
1300275738
57.72588
11.84981
0.000263888888888888
1300275780
57.72645
11.85242
0.001013888888888888
.
.

有谁知道如何将我的临时表转换回按每组四个中的第一个值排序的逗号分隔字符串？

4

2 回答 2

0 
;WITH cte(car_Id, traceXML) AS
 (
  SELECT car_Id, CAST('<A>' + REPLACE(trace, ';', '</A><A>') + '</A>' AS XML)
  FROM dbo.cars
  ), cte2 AS
 (
  SELECT car_Id, trace, NTILE(4) OVER(ORDER BY (SELECT 1)) AS grId  
  FROM cte
  CROSS APPLY (SELECT Tbl.Col.value('.', 'nvarchar(250)') AS trace 
               FROM traceXML.nodes('/A') Tbl(Col)) AS List
  ), cte3 AS
 (
  SELECT DISTINCT a.car_Id,(
  SELECT ISNULL(b.trace, '') + ';' 
  FROM cte2 b 
  WHERE b.grId = a.grId
  FOR XML PATH('')) AS trace
  FROM cte2 a
  )
  SELECT DISTINCT a.car_Id,(
  SELECT ISNULL(b.trace, '')
  FROM cte3 b
  WHERE b.car_Id = a.car_Id
  FOR XML PATH('')) AS trace
  FROM cte3 a

SQLFiddle上的演示

于 2012-12-03T23:45:06.320 回答
0

我最终使用了两个函数和一个触发器。

首先是一个将跟踪字符串拆分为行的函数

CREATE FUNCTION dbo.Split(@String varchar(MAX))       
returns @temptable TABLE (items varchar(MAX)) 
as       
begin       
    declare @idx int       
    declare @idx2 int
    declare @idx3 int
    declare @idx4 int
    declare @slice varchar(8000)

    select @idx = 1       
        if len(@String)<1 or @String is null  return       

    while @idx != 0       
    begin       
        set @idx = charindex(';',@String)       
        if @idx!=0       
            set @slice = left(@String,@idx)       
        else       
            set @slice = @String       

        set @String = right(@String,len(@String) - @idx)
        set @idx2 = charindex(';',@String);

        if @idx2!=0       
            set @slice = @slice + left(@String,@idx2)

        set @String = right(@String,len(@String) - @idx2)
        set @idx3 = charindex(';',@String);

        if @idx3!=0       
            set @slice = @slice + left(@String,@idx3)

        set @String = right(@String,len(@String) - @idx3)
        set @idx4 = charindex(';',@String);

        if @idx4 !=0       
            set @slice = @slice + left(@String,@idx4)
        else
            set @slice = @slice + @String

        if(len(@slice)>0)
            insert into @temptable(Items) values(@slice)       

        set @String = right(@String,len(@String) - @idx4) 
        if len(@String) = 0 break
        if @idx4 = 0 break   
    end
return      
end

然后是一个对临时表中的行进行排序和合并的函数

CREATE FUNCTION dbo.SortCSV(@String varchar(MAX))       
returns varchar(MAX)
as
begin
    declare @csv varchar(MAX)
    select @csv = coalesce(@csv,'') + items
    from dbo.Split(@String)
    order by items asc
return @csv
end

最后我创建了一个这样的触发器

CREATE TRIGGER dbo.SortTrace 
   ON  dbo.trips 
   INSTEAD OF INSERT
AS 
BEGIN
    -- SET NOCOUNT ON added to prevent extra result sets from
    -- interfering with SELECT statements.
    SET NOCOUNT ON;

    DECLARE @trace varchar(MAX);
    DECLARE @sorted_trace varchar(MAX);

    SELECT @trace = trace FROM inserted;
    SELECT @sorted_trace = dbo.SortCSV(@trace);

    insert into dbo.trips (
        car_id, start, stop, distance, created_at, updated_at, trace, energy, delta_soc, private_trip, journal_comment
    ) select
        car_id, start, stop, distance, created_at, updated_at, @sorted_trace, energy, delta_soc, private_trip, journal_comment
    from
        inserted
END
GO
于 2012-12-04T07:18:14.950 回答