Dynamically concatenate string

Question

Dynamically concatenate string

curious_sqldba

SSC-Dedicated

Points: 36494
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August 28, 2019 at 2:20 am

#3674921
I have a below sample t-sql, i am trying to dynamically concatenate the rows, the number of rows can vary . Any pointers would be helpful.
```
drop table if exists #T1



create table #T1
(

FileName char(400)
)


Insert into #T1
select 'ABC'

Insert into #T1
Select 'DEF'

select * from #T1

-- Desired output: filename='ABC',filename='DEF'
```

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DesNorton SSC-Insane Points: 24278 More actions · Answer 1

This will concatenate the values as per the sample data

SELECT STUFF((
          SELECT ',filename=''' + RTRIM(FileName) + ''''
          FROM #T1
          FOR XML PATH('')
          ), 1, 1, '')

How to post data/code on a forum to get the best help.

Jeff Moden SSC Guru Points: 1003863 More actions · Answer 2

Whatever method you're trying, you're probably running into problems because you've defined the [FileName] column as a CHAR(400). For the value of "ABC", that means the row contains "ABC" followed by 397 spaces, which messes up concatenation attempts. You just need to do an RTRIM on the [FileName] value to make it work... like this...

 SELECT DISTINCT
        DesiredOutput = STUFF(
                                (
                                 SELECT ',filename='+RTRIM(t1.[FileName])
                                   FROM #T1 t1
                                    FOR XML PATH(''),TYPE
                                ).value('(./text())[1]','VARCHAR(MAX)')
                        ,1,1,'')
   FROM #T1 t2
;

Either that or define the [FileName] column as a VARCHAR(400) instead of a CHAR(400).

--Jeff Moden

RBAR is pronounced "ree-bar" and is a "Modenism" for Row-By-Agonizing-Row.
First step towards the paradigm shift of writing Set Based code:
________Stop thinking about what you want to do to a ROW... think, instead, of what you want to do to a COLUMN.

Change is inevitable... Change for the better is not.

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