How to Transform Comma-Separated Values in a SQL Column into Separate Rows?-Mysql Tutorial-php.cn

How to Transform Comma-Separated Values in a SQL Column into Separate Rows?

Mary-Kate Olsen

Release： 2025-01-05 10:06:45

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How to Transform Comma-Separated Values in a SQL Column into Separate Rows?

Querying SQL to Divide Column Data into Rows

Problem:

You have a table with two columns, Code and Declaration. The Declaration column contains a comma-separated list of values. You need to convert this data into rows, with each row representing a separate declaration for the corresponding code.

Solution:

One approach to address this issue involves creating a custom SQL function:

create FUNCTION [dbo].[Split](@String varchar(MAX), @Delimiter char(1))       
returns @temptable TABLE (items varchar(MAX))       
as       
begin      
    declare @idx int       
    declare @slice varchar(8000)       

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

    while @idx!= 0       
    begin       
        set @idx = charindex(@Delimiter,@String)       
        if @idx!=0       
            set @slice = left(@String,@idx - 1)       
        else       
            set @slice = @String       

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

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

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You can then leverage this function in a query using an outer apply to connect to your existing table:

select t1.code, s.items declaration
from yourtable t1
outer apply dbo.split(t1.declaration, ',') s

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This query will produce the desired result:

| CODE |  DECLARATION |
-----------------------
|  123 |     a1-2 nos |
|  123 |  a2- 230 nos |
|  123 |    a3 - 5nos |

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Alternatively, you can use a CTE (Common Table Expression) version, which operates similarly:

;with cte (code, DeclarationItem, Declaration) as
(
  select Code,
    cast(left(Declaration, charindex(',',Declaration+',')-1) as varchar(50)) DeclarationItem,
         stuff(Declaration, 1, charindex(',',Declaration+','), '') Declaration
  from yourtable
  union all
  select code,
    cast(left(Declaration, charindex(',',Declaration+',')-1) as varchar(50)) DeclarationItem,
    stuff(Declaration, 1, charindex(',',Declaration+','), '') Declaration
  from cte
  where Declaration > ''
) 
select code, DeclarationItem
from cte

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