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

这个模式工作得很好,可以进行推广

Convert(xml,'<n>'+Replace(FIELD,'.','</n><n>')+'</n>').value('(/n[INDEX])','TYPE')
                          ^^^^^                                   ^^^^^     ^^^^

注意字段,索引和类型。

让一些表具有类似的标识符

sys.message.1234.warning.A45
sys.message.1235.error.O98
....

然后,你就可以写作了

SELECT Source         = q.value('(/n[1])', 'varchar(10)'),
       RecordType     = q.value('(/n[2])', 'varchar(20)'),
       RecordNumber   = q.value('(/n[3])', 'int'),
       Status         = q.value('(/n[4])', 'varchar(5)')
FROM   (
         SELECT   q = Convert(xml,'<n>'+Replace(fieldName,'.','</n><n>')+'</n>')
         FROM     some_TABLE
       ) Q

拆铸所有零件。

其他回答

一个简单的优化算法:

ALTER FUNCTION [dbo].[Split]( @Text NVARCHAR(200),@Splitor CHAR(1) )
RETURNS @Result TABLE ( value NVARCHAR(50)) 
AS
BEGIN
    DECLARE @PathInd INT
    Set @Text+=@Splitor
    WHILE LEN(@Text) > 0
    BEGIN
        SET @PathInd=PATINDEX('%'+@Splitor+'%',@Text)
        INSERT INTO  @Result VALUES(SUBSTRING(@Text, 0, @PathInd))
        SET @Text= SUBSTRING(@Text, @PathInd+1, LEN(@Text))
    END
        RETURN 
END

修改@Aaron Bertrand的功能

CREATE FUNCTION [dbo].[SplitString]
(
    @List NVARCHAR(MAX),
    @Delim VARCHAR(255),
    @Idx int
)
RETURNS NVARCHAR(1000)
AS
BEGIN
    DECLARE @ValueTable TABLE(String NVARCHAR(50), Ind int)
    DECLARE @Value NVARCHAR(50)
    BEGIN
    INSERT INTO @ValueTable
    SELECT Value, idx FROM
        (SELECT [Value], idx = RANK() OVER (ORDER BY n) FROM 
              ( 
                SELECT n = Number, 
                [Value] = LTRIM(RTRIM(SUBSTRING(@List, [Number],
                CHARINDEX(@Delim, @List + @Delim, [Number]) - [Number])))
                FROM    
                        (SELECT Number = ROW_NUMBER() OVER (ORDER BY name)
                         FROM sys.all_objects) AS x
                WHERE Number <= LEN(@List)
                AND SUBSTRING(@Delim + @List, [Number], LEN(@Delim)) = @Delim
              ) AS y
          ) AS R WHERE idx = @Idx
    SET @Value = (SELECT String FROM @ValueTable)
    END
    RETURN @Value
END
GO

在这里我发布了一个简单的解决方法

CREATE FUNCTION [dbo].[split](
          @delimited NVARCHAR(MAX),
          @delimiter NVARCHAR(100)
        ) RETURNS @t TABLE (id INT IDENTITY(1,1), val NVARCHAR(MAX))
        AS
        BEGIN
          DECLARE @xml XML
          SET @xml = N'<t>' + REPLACE(@delimited,@delimiter,'</t><t>') + '</t>'

          INSERT INTO @t(val)
          SELECT  r.value('.','varchar(MAX)') as item
          FROM  @xml.nodes('/t') as records(r)
          RETURN
        END

像这样执行函数

  select * from dbo.split('Hello John Smith',' ')

基于纯集的解决方案,使用TVF和递归CTE。您可以将此函数JOIN和APPLY到任何数据集。

create function [dbo].[SplitStringToResultSet] (@value varchar(max), @separator char(1))
returns table
as return
with r as (
    select value, cast(null as varchar(max)) [x], -1 [no] from (select rtrim(cast(@value as varchar(max))) [value]) as j
    union all
    select right(value, len(value)-case charindex(@separator, value) when 0 then len(value) else charindex(@separator, value) end) [value]
    , left(r.[value], case charindex(@separator, r.value) when 0 then len(r.value) else abs(charindex(@separator, r.[value])-1) end ) [x]
    , [no] + 1 [no]
    from r where value > '')

select ltrim(x) [value], [no] [index] from r where x is not null;
go

用法:

select *
from [dbo].[SplitStringToResultSet]('Hello John Smith', ' ')
where [index] = 1;

结果:

value   index
-------------
John    1

我知道已经晚了,但我最近有了这个需求,并提出了下面的代码。我没有选择使用用户定义的函数。希望这能有所帮助。

SELECT 
    SUBSTRING(
                SUBSTRING('Hello John Smith' ,0,CHARINDEX(' ','Hello John Smith',CHARINDEX(' ','Hello John Smith')+1)
                        ),CHARINDEX(' ','Hello John Smith'),LEN('Hello John Smith')
            )