SQL create distinct comma separated lists - sql

Question

I have a stored procedures that accepts a comma separated list, then makes copies of that list with quoted strings and brackets, then uses those in a dynamic sql statement to build a pivot table with flexible number of columns.
My problem is that sometimes my users submit a list with duplicates, and that makes the pivot query fail. So I want to somehow select distinct from my comma separated strings.
Here's how I manipulate the initial string:
Declare #data varchar(max) = '150593, 150593, 150603, 150578, 150604'
Declare #bracketed varchar(max) = ''
Declare #quoted varchar(max) = ''
select #bracketed = #bracketed + quotename(rtrim(ltrim(Value))) + ', ',
#quoted = #quoted + quotename(rtrim(ltrim(Value)), '''') + ', '
from [dbo].[fnSplitStringAsTable](#data, ',')
Select #bracketed = LEFT(#bracketed, len(#bracketed) - 1),
#quoted = LEFT(#quoted, len(#quoted) - 1)
I'm thinking I should be able to add DISTINCT somewhere in this query,
but I can't make it work. How can I select distinct from comma separated lists?

Answer 1

as an alternative solution you can dedupe in xml and convert back to varchar
Declare #data varchar(max) = '150593, 150593, 150603, 150578, 150604'
set #data= (select '''' + cast(cast('<d>'+replace(#data, ', ',',</d><d>')+'</d>' as xml).query('distinct-values(/d)') as varchar) +'''')
select #data

Answer 2

I guess we can add in distinct after you make the table, like this:
select #bracketed = #bracketed + quotename(rtrim(ltrim(Value))) + ', ',
#quoted = #quoted + quotename(rtrim(ltrim(Value)), '''') + ', '
from (
SELECT DISTINCT Value FROM [dbo].[fnSplitStringAsTable](#data, ',')
) T
If this fails try this:
select #bracketed = #bracketed + quotename(Value) + ', ',
#quoted = #quoted + quotename(Value), '''') + ', '
from (
SELECT DISTINCT RTRIM(LTRIM(Value)) AS Value FROM [dbo].[fnSplitStringAsTable](#data, ',')
) T

Answer 3

With a little dynamic sql, you can select distinct values from your string variable into a table variable, and then put those values back into the original variable:
declare #data varchar(max) = '150593, 150593, 150603, 150578, 150604'
declare #table table(data varchar(10))
set #data = 'select distinct value from (values (''' +
replace(#data,', ','''),(''') + ''')) as v(value)'
insert into #table
exec(#data)
set #data = ''
select #data = #data + data +
case row_number() over(order by data desc)
when 1 then ''
else ','
end
from #table
order by data asc
select #data