Question

mytable structure: id int, lookuptablename varchar

1, 'lookuptable1'
2, 'lookuptable2'

lookuptable1: id int, item varchar

1, 'item1 from lkt1'
2, 'item2 from lkt1'

lookuptable2: id int, item varchar

1, 'item1 from lkt2'
2, 'item2 from lkt2'

Query:

SELECT GetDelimitedList(lookuptablename) FROM mytable;

Expected result:

1,2~item1 from lkt1,item2 from lkt1
1,2~item1 from lkt2,item2 from lkt2

I have been struggling to find out a way to accomplish this in various ways but just couldn’t figure it out.

Answer 1

A workaround. UDFs won’t work. Maybe CLR, but not native SQL UDF.

First create this proc, which mashes a table into a single row

create proc dbo.GetDelimitedList
@tablename sysname
AS
declare @sql nvarchar(max)
set @sql = '
declare @id nvarchar(max), @item nvarchar(max)
select
    @id = isnull(@id+'','','''') + convert(varchar,id),
    @item = isnull(@item+'','','''') + item
from ' + quotename(@tablename) + '
select @id + ''~'' + @item'
exec (@sql)
GO

Then use this SQL batch to produce the output equivalent to SELECT GetDelimitedList(tablename) FROM mytable;

declare @tmp table(id int, mashed nvarchar(max))
declare @id int, @tablename sysname
-- start at first table
select top 1 @id = id, @tablename = tablename
from mytable
order by id asc
while @@ROWCOUNT > 0
begin
    -- fill our temp table
    insert @tmp (mashed) exec GetDelimitedList 'mytablelist'
    update @tmp set id = @id where id is null
    -- next table
    select top 1 @id=id, @tablename = tablename
    from mytable
    where id > @id
    order by id asc
end
SELECT * FROM @tmp;

Sample tables used:

create table mytable(id int, tablename varchar(100))
insert mytable values (1, 'mytablelist')
insert mytable values (3, 'mytablelist2')

create table mytablelist(id int, item varchar(100))
insert mytablelist values
(1, 'item1'),
(2, 'item2')
GO

create table mytablelist2(id int, item varchar(100))
insert mytablelist2 values
(11, 't2item1'),
(22, 't2item2')
GO