使用SQL Server,我如何分割一个字符串,以便我可以访问项目x?

拿一根“你好,约翰·史密斯”的绳子。我如何通过空格分割字符串并访问索引1应该返回“约翰”的项目?


当前回答

这里有一个UDF可以做到这一点。它将返回一个带分隔符的值的表,我还没有尝试所有的场景,但您的示例工作良好。


CREATE FUNCTION SplitString 
(
    -- Add the parameters for the function here
    @myString varchar(500),
    @deliminator varchar(10)
)
RETURNS 
@ReturnTable TABLE 
(
    -- Add the column definitions for the TABLE variable here
    [id] [int] IDENTITY(1,1) NOT NULL,
    [part] [varchar](50) NULL
)
AS
BEGIN
        Declare @iSpaces int
        Declare @part varchar(50)

        --initialize spaces
        Select @iSpaces = charindex(@deliminator,@myString,0)
        While @iSpaces > 0

        Begin
            Select @part = substring(@myString,0,charindex(@deliminator,@myString,0))

            Insert Into @ReturnTable(part)
            Select @part

    Select @myString = substring(@mystring,charindex(@deliminator,@myString,0)+ len(@deliminator),len(@myString) - charindex(' ',@myString,0))


            Select @iSpaces = charindex(@deliminator,@myString,0)
        end

        If len(@myString) > 0
            Insert Into @ReturnTable
            Select @myString

    RETURN 
END
GO

你可以这样称呼它:


Select * From SplitString('Hello John Smith',' ')

编辑:使用len>1处理分隔符的更新解决方案如下:


select * From SplitString('Hello**John**Smith','**')

其他回答

下面的示例使用递归CTE

更新18.09.2013

CREATE FUNCTION dbo.SplitStrings_CTE(@List nvarchar(max), @Delimiter nvarchar(1))
RETURNS @returns TABLE (val nvarchar(max), [level] int, PRIMARY KEY CLUSTERED([level]))
AS
BEGIN
;WITH cte AS
 (
  SELECT SUBSTRING(@List, 0, CHARINDEX(@Delimiter,  @List + @Delimiter)) AS val,
         CAST(STUFF(@List + @Delimiter, 1, CHARINDEX(@Delimiter, @List + @Delimiter), '') AS nvarchar(max)) AS stval, 
         1 AS [level]
  UNION ALL
  SELECT SUBSTRING(stval, 0, CHARINDEX(@Delimiter, stval)),
         CAST(STUFF(stval, 1, CHARINDEX(@Delimiter, stval), '') AS nvarchar(max)),
         [level] + 1
  FROM cte
  WHERE stval != ''
  )
  INSERT @returns
  SELECT REPLACE(val, ' ','' ) AS val, [level]
  FROM cte
  WHERE val > ''
  RETURN
END

演示SQLFiddle



    Alter Function dbo.fn_Split
    (
    @Expression nvarchar(max),
    @Delimiter  nvarchar(20) = ',',
    @Qualifier  char(1) = Null
    )
    RETURNS @Results TABLE (id int IDENTITY(1,1), value nvarchar(max))
    AS
    BEGIN
       /* USAGE
            Select * From dbo.fn_Split('apple pear grape banana orange honeydew cantalope 3 2 1 4', ' ', Null)
            Select * From dbo.fn_Split('1,abc,"Doe, John",4', ',', '"')
            Select * From dbo.fn_Split('Hello 0,"&""&&&&', ',', '"')
       */

       -- Declare Variables
       DECLARE
          @X     xml,
          @Temp  nvarchar(max),
          @Temp2 nvarchar(max),
          @Start int,
          @End   int

       -- HTML Encode @Expression
       Select @Expression = (Select @Expression For XML Path(''))

       -- Find all occurences of @Delimiter within @Qualifier and replace with |||***|||
       While PATINDEX('%' + @Qualifier + '%', @Expression) > 0 AND Len(IsNull(@Qualifier, '')) > 0
       BEGIN
          Select
             -- Starting character position of @Qualifier
             @Start = PATINDEX('%' + @Qualifier + '%', @Expression),
             -- @Expression starting at the @Start position
             @Temp = SubString(@Expression, @Start + 1, LEN(@Expression)-@Start+1),
             -- Next position of @Qualifier within @Expression
             @End = PATINDEX('%' + @Qualifier + '%', @Temp) - 1,
             -- The part of Expression found between the @Qualifiers
             @Temp2 = Case When @End < 0 Then @Temp Else Left(@Temp, @End) End,
             -- New @Expression
             @Expression = REPLACE(@Expression,
                                   @Qualifier + @Temp2 + Case When @End < 0 Then '' Else @Qualifier End,
                                   Replace(@Temp2, @Delimiter, '|||***|||')
                           )
       END

       -- Replace all occurences of @Delimiter within @Expression with '</fn_Split>&ltfn_Split>'
       -- And convert it to XML so we can select from it
       SET
          @X = Cast('&ltfn_Split>' +
                    Replace(@Expression, @Delimiter, '</fn_Split>&ltfn_Split>') +
                    '</fn_Split>' as xml)

       -- Insert into our returnable table replacing '|||***|||' back to @Delimiter
       INSERT @Results
       SELECT
          "Value" = LTRIM(RTrim(Replace(C.value('.', 'nvarchar(max)'), '|||***|||', @Delimiter)))
       FROM
          @X.nodes('fn_Split') as X(C)

       -- Return our temp table
       RETURN
    END

建立在@NothingsImpossible解决方案上,或者,更确切地说,评论投票最多的答案(就在接受的答案下面),我发现下面的快速和肮脏的解决方案满足了我自己的需求-它的好处是完全在SQL域内。

给定一个字符串"first;second;third;fourth;fifth",比如说,我想获取第三个标记。只有当我们知道字符串将有多少标记时,这才有效——在这种情况下,它是5。所以我的操作方式是将最后两个令牌切掉(内部查询),然后将前两个令牌切掉(外部查询)

我知道这是丑陋的,涵盖了我所处的具体情况,但我张贴它只是为了以防有人发现它有用。干杯

select 
    REVERSE(
        SUBSTRING(
            reverse_substring, 
            0, 
            CHARINDEX(';', reverse_substring)
        )
    ) 
from 
(
    select 
        msg,
        SUBSTRING(
            REVERSE(msg), 
            CHARINDEX(
                ';', 
                REVERSE(msg), 
                CHARINDEX(
                    ';',
                    REVERSE(msg)
                )+1
            )+1,
            1000
        ) reverse_substring
    from 
    (
        select 'first;second;third;fourth;fifth' msg
    ) a
) b

几乎所有其他答案都是替换正在分割的字符串,这浪费了CPU周期并执行不必要的内存分配。

我在这里介绍了一种更好的进行字符串拆分的方法:http://www.digitalruby.com/split-string-sql-server/

代码如下:

SET NOCOUNT ON

-- You will want to change nvarchar(MAX) to nvarchar(50), varchar(50) or whatever matches exactly with the string column you will be searching against
DECLARE @SplitStringTable TABLE (Value nvarchar(MAX) NOT NULL)
DECLARE @StringToSplit nvarchar(MAX) = 'your|string|to|split|here'
DECLARE @SplitEndPos int
DECLARE @SplitValue nvarchar(MAX)
DECLARE @SplitDelim nvarchar(1) = '|'
DECLARE @SplitStartPos int = 1

SET @SplitEndPos = CHARINDEX(@SplitDelim, @StringToSplit, @SplitStartPos)

WHILE @SplitEndPos > 0
BEGIN
    SET @SplitValue = SUBSTRING(@StringToSplit, @SplitStartPos, (@SplitEndPos - @SplitStartPos))
    INSERT @SplitStringTable (Value) VALUES (@SplitValue)
    SET @SplitStartPos = @SplitEndPos + 1
    SET @SplitEndPos = CHARINDEX(@SplitDelim, @StringToSplit, @SplitStartPos)
END

SET @SplitValue = SUBSTRING(@StringToSplit, @SplitStartPos, 2147483647)
INSERT @SplitStringTable (Value) VALUES(@SplitValue)

SET NOCOUNT OFF

-- You can select or join with the values in @SplitStringTable at this point.

首先,创建一个函数(使用CTE,公共表表达式不再需要临时表)

 create function dbo.SplitString 
    (
        @str nvarchar(4000), 
        @separator char(1)
    )
    returns table
    AS
    return (
        with tokens(p, a, b) AS (
            select 
                1, 
                1, 
                charindex(@separator, @str)
            union all
            select
                p + 1, 
                b + 1, 
                charindex(@separator, @str, b + 1)
            from tokens
            where b > 0
        )
        select
            p-1 zeroBasedOccurance,
            substring(
                @str, 
                a, 
                case when b > 0 then b-a ELSE 4000 end) 
            AS s
        from tokens
      )
    GO

然后,像这样使用它作为任何表(或修改它以适应现有存储的proc)。

select s 
from dbo.SplitString('Hello John Smith', ' ')
where zeroBasedOccurance=1

更新

以前的版本将失败的输入字符串长度超过4000个字符。这个版本考虑到了以下限制:

create function dbo.SplitString 
(
    @str nvarchar(max), 
    @separator char(1)
)
returns table
AS
return (
with tokens(p, a, b) AS (
    select 
        cast(1 as bigint), 
        cast(1 as bigint), 
        charindex(@separator, @str)
    union all
    select
        p + 1, 
        b + 1, 
        charindex(@separator, @str, b + 1)
    from tokens
    where b > 0
)
select
    p-1 ItemIndex,
    substring(
        @str, 
        a, 
        case when b > 0 then b-a ELSE LEN(@str) end) 
    AS s
from tokens
);

GO

用法不变。