Question

I have a tough programming problem in SQL Server 2000 that I’m hoping I can get help with. I am a novice with T-SQL (I mostly use MySQL) so maybe someone could look at this and see an easy way to do it.

I have a table with lots of columns that contain either a 0 or 1. For example, I have columns labeled var1, var2, var5, var9. etc. up to about 120 columns total. Notice that the suffixes on these columns aren’t necessarily consecutive. Each of these columns contain a 0 or 1. What I need to do is create a new column the contains the literal column names of every column that contains a 1.

For example, my data look like this:

ID var1   var2   var5    var7   var9
--------------------------------------
1    0      1      0      0       1
2    0      1      1      1       0

I need a new column that contains the values

ID  NewCol
---------------------
1   var2,var9
2   var2,var5,var7

and so on.

For reasons I won’t go in to, I can’t use any client side code like VB, Perl, etc. I have to do this in a stored procedure. Due to the large number of columns that could change in either name or number, I need something other than a hardcoded series of SELECT CASE statements.

I feel really limited by my T-SQL knowledge. Can this be done??

TIA

Answer 1

You can do this with a query that looks like this:

select ID,
       stuff(
       case var1 when 1 then ',var1' else '' end +
       case var2 when 1 then ',var2' else '' end +
       case var5 when 1 then ',var5' else '' end +
       case var7 when 1 then ',var7' else '' end +
       case var9 when 1 then ',var9' else '' end
       , 1, 1, '')
from YourTable

Here is a way to build it dynamically.

declare @SQL varchar(8000)
set @SQL = ''

select @SQL = @SQL + ' + case '+COLUMN_NAME+' when 1 then '','+COLUMN_NAME+''' else '''' end'
from INFORMATION_SCHEMA.COLUMNS
where TABLE_NAME = 'YourTable' and
      COLUMN_NAME <> 'ID'

set @SQL = 'select ID, stuff('+stuff(@SQL, 1, 3, '')+', 1, 1, '''') from YourTable'

exec(@SQL)