Loop in stored procedure in SQL server

Here's an example of how you can use cursors to do loops:

-- set up some test data
declare @table_a table (PK_TableA_ID int)
declare @table_b table (PK_TableB_ID int)
insert @table_a values (1),(2),(3)
insert @table_b values (4),(5),(6)    

-- do the actual processing
SET NOCOUNT ON

DECLARE @TableA_ID int, @TableB_ID int

DECLARE TableA_cursor CURSOR FOR SELECT PK_TableA_ID FROM @table_a

OPEN TableA_cursor
FETCH NEXT FROM TableA_cursor INTO @TableA_ID

WHILE @@FETCH_STATUS = 0
BEGIN
    DECLARE TableB_cursor CURSOR FOR SELECT PK_TableB_ID FROM @table_b

    OPEN TableB_cursor
    FETCH NEXT FROM TableB_cursor INTO @TableB_ID

    WHILE @@FETCH_STATUS = 0
    BEGIN
        PRINT CAST(@TableA_ID AS CHAR(1)) + ':' + CAST(@TableB_ID AS CHAR(1))
        -- execute your stored procedure here:
        -- EXEC Your_stored_procedure (@TableA_ID, @TableB_ID) 
        FETCH NEXT FROM TableB_cursor INTO @TableB_ID
        END

    CLOSE TableB_cursor
    DEALLOCATE TableB_cursor

    FETCH NEXT FROM TableA_cursor INTO @TableA_ID
END 
CLOSE TableA_cursor
DEALLOCATE TableA_cursor

The cursor above (with the test data in the temporary tables) will generate this output:

1:4
1:5
1:6
2:4
2:5
2:6
3:4
3:5
3:6

Using cursors might not be the best way to solve your problem though.

I have a clean and clear option without cursors for this case using the table ids.

DECLARE 
@Counter1 INT,@MaxId1 INT,
@Counter2 INT, @MaxId2 INT 

SELECT @Counter1 = min(PK_TableA_ID) , @MaxId1 = max(PK_TableA_ID) 
FROM TableA
SELECT @Counter2 = min(PK_TableB_ID) , @MaxId2 = max(PK_TableB_ID) 
FROM TableB

WHILE(@Counter1 IS NOT NULL AND @Counter1 <= @MaxId1)
BEGIN 
      WHILE(@Counter2 IS NOT NULL AND @Counter2 <= @MaxId2)
      BEGIN
          //call stored procedure 
          SP1(@Counter1, @Counter2);

          SET @Counter2  = @Counter2  + 1
      END;
      
      SELECT @Counter2 = min(PK_TableB_ID) , @MaxId2 = max(PK_TableB_ID) 
      FROM TableB
      SET @Counter1  = @Counter1  + 1             
END;