Question

How can i add new column in a temporary table based on the query result. Consider the code below

declare @ctr int
set @ctr = 1

while (@ctr <= (select count(*) from #temp2)
begin
  alter table #temp
  add (select t2.Value from #temp2 t2 where t2.SysID = @ctr) (select t2.Type from #temp3 t3 where t3.SysID = @ctr)
end

something like that. I have some syntax error about this but as far as i know my syntax is correct

Answer 1

you’ll have to use dynamic SQL. This is something that I have done before:

SET @sql = 'ALTER TABLE ' + @TableName +
           'ADD ' + CONVERT(VARCHAR(100), @ColName) + ' ' + 
           CONVERT(VARCHAR(100), @TypeName) + 
           CASE WHEN @TypeName IN ('int', 'datetime', 'money', 'uniqueidentifier', 'bit')
                THEN '' ELSE '(' + CONVERT(VARCHAR(10), @Prec) + ')' END + ' NULL'

EXEC(@sql)

this probably doesn’t cover every possible datatype but for my requirements, it was enough. In any case, a good place to start