Cross Join 'n' times a table

Question

It is possible to write a generic function/procedure/select/somethingElse to cross-join a table against himself 'n' times? (yes, 'n' is a given parameter : )

How would you do it?

---

Example

Having this table:

 Value
-------
   1
   2
   3 

cross join it 2 times, would return:

 Value  | Value
------------------
    1       1
    1       2
    1       3
    2       1
    2       2
    2       3
    3       1
    3       2
    3       3

Answer 1

You can generate dynamic sql to output as many cross joins as you need:

create table #t (value int)

insert into #t values (1)
insert into #t values (2)
insert into #t values (3)

declare @n int
set @n = 4

declare @sql varchar(max)
set @sql = 'SELECT * FROM #t t'
declare @i int
set @i = 0
while (@i <= @n)
begin
    set @sql = @sql + ' cross join #t t' + CAST(@i as varchar)
    set @i = @i + 1
end

print @sql
execute(@sql)

drop table #t

Answer 2

Using dynamic SQL, SQL Server 2005+ (@table_name and @numCrossJoins are stored procedure parameters):

DECLARE @upperLimit INT
    SET @upperLimit = 1

DECLARE @SQL NVARCHAR(MAX)
    SET @SQL = 'SELECT * FROM '+ @table_name +' '

BEGIN 

  WHILE (upperLimit <= @numCrossJoins)
  BEGIN

    SET @SQL = @SQL + 'CROSS JOIN '+ @table_name +' '

    SET @upperLimit = @upperLimit + 1
  END

  EXEC sp_executesql @SQL

END

Answer 3

If you need to come up with all possible permutations, here is an example:

All Permutations For A String

Answer 4

Try this:

SET @SQL = 'SELECT * FROM ' + replicate('[' + @table_name + '],', @N);

set @SQL = LEFT(LEN(@SQL) - 1);

EXEC sp_executesql @SQL;