SQL Sting Split into Single Column

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深忆病人
深忆病人 2021-01-28 14:30

Very new to SQL but I require some help with something that I am sure is a simple fix.

I have a single column of data within a table called \'Produce\' where types of fr

2条回答
  •  -上瘾入骨i
    2021-01-28 14:50

    The core problem to fix would be to stop storing your values as comma separated lists. Keep your data normalized. With that being said... everyone needs a good splitter...

    declare @table table (Fruit varchar(64))
    insert into @table
    values
    ('Apple'),
    ('Plum'),
    ('Pear,Mango'),
    ('Pear')
    
    select distinct
        Item
    from
        @table
    cross apply
        dbo.DelimitedSplit8K(Fruit,',')
    

    OR, If you are on SQL Server 2016...

    select distinct
        Item
    from
        @table
    cross apply
        string_split(Fruit,',')
    

    THE FUNCTION

    SET ANSI_NULLS ON
    GO
    
    SET QUOTED_IDENTIFIER ON
    GO
    
    CREATE FUNCTION [dbo].[DelimitedSplit8K] (@pString VARCHAR(8000), @pDelimiter CHAR(1))
    --WARNING!!! DO NOT USE MAX DATA-TYPES HERE!  IT WILL KILL PERFORMANCE!
    
    RETURNS TABLE WITH SCHEMABINDING AS
    RETURN
    
    /* "Inline" CTE Driven "Tally Table" produces values from 1 up to 10,000...
    enough to cover VARCHAR(8000)*/
    
      WITH E1(N) AS (
                     SELECT 1 UNION ALL SELECT 1 UNION ALL SELECT 1 UNION ALL
                     SELECT 1 UNION ALL SELECT 1 UNION ALL SELECT 1 UNION ALL
                     SELECT 1 UNION ALL SELECT 1 UNION ALL SELECT 1 UNION ALL SELECT 1
                    ),                          --10E+1 or 10 rows
           E2(N) AS (SELECT 1 FROM E1 a, E1 b), --10E+2 or 100 rows
           E4(N) AS (SELECT 1 FROM E2 a, E2 b), --10E+4 or 10,000 rows max
     cteTally(N) AS (--==== This provides the "base" CTE and limits the number of rows right up front
                         -- for both a performance gain and prevention of accidental "overruns"
                     SELECT TOP (ISNULL(DATALENGTH(@pString),0)) ROW_NUMBER() OVER (ORDER BY (SELECT NULL)) FROM E4
                    ),
    cteStart(N1) AS (--==== This returns N+1 (starting position of each "element" just once for each delimiter)
                     SELECT 1 UNION ALL
                     SELECT t.N+1 FROM cteTally t WHERE SUBSTRING(@pString,t.N,1) = @pDelimiter
                    ),
    cteLen(N1,L1) AS(--==== Return start and length (for use in substring)
                     SELECT s.N1,
                            ISNULL(NULLIF(CHARINDEX(@pDelimiter,@pString,s.N1),0)-s.N1,8000)
                       FROM cteStart s
                    )
    --===== Do the actual split. The ISNULL/NULLIF combo handles the length for the final element when no delimiter is found.
     SELECT ItemNumber = ROW_NUMBER() OVER(ORDER BY l.N1),
            Item       = SUBSTRING(@pString, l.N1, l.L1)
       FROM cteLen l
    ;
    GO
    

    Jeff Moden Article for Function

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