SQL Server loop through dynamic query

Question

I have a procedure where I pass temporary table name as parameter. For each dataset inside I need to get rowcount. How to achieve this?

I need something like:

CREATE PROCEDURE sp_processing 
  @temp_table_name varchar(50)
AS
  DECLARE @log varchar(max)

/* get list of keys inside temp_table_name */
/* just a pseudo-code example */
SET @l_cursor = CURSOR FOR 
SELECT Key1, Key2, Key3, count(*) 
  FROM @temp_table_name -- table name passed as text 
 GROUP by Key1, Key2, Key3;

WHILE "there are results"
BEGIN
  @log += @Key1 +', '+ @Key2 +', '+ @Key3 +', '+ @count + CHAR(13)+CHAR(10);
END

UPDATE log_table SET log_column = @log WHERE....;

END /* procedure */

Is there a way to loop this?

I know I have option to fetch results to a table type and THEN loop, but that requires to use a table type, so wondering if this is achievable without a table variable.

EDIT: I need just need to print count for each set of keys.

Answer 1

This worked for me:

DECLARE @l_sql nvarchar(max)
DECLARE @temp_table_name varchar(50) = 'SOME_TABLE'
DECLARE @combinedString varchar(max)
SET @l_sql = 'SELECT @combinedString = COALESCE(@combinedString, '''') + convert(varchar,[Key1]) +'', ''+ convert(varchar,[Key3]) +'': ''+ convert(varchar,COUNT(*)) + ''| '' + CHAR(13)+CHAR(10) '
           + '  FROM ' + @temp_table_name  
           + ' GROUP BY [Key1], [Key3]'
           + ' ORDER BY [Key1], [Key3]';

EXECUTE sp_executesql @l_sql, N'@combinedString varchar(max) OUTPUT', @combinedString = @combinedString OUTPUT ;

SELECT @combinedString 

Result:

1, 1: 4| 
1, 2: 2| 
1, 3: 1| 
2, 5: 1|