create extra column/mark column if match found in table a vs table b with loops

Hi,

Would be really nice if someone could help me out on the following problem. There are 2 tables: table A vs. Table B. where certain columns are the same. I have tried to make a loop to take out or at least mark the matches in an extra column.

The procedure that i want: take the 1st row from table A. and loop over table B for matches, if found than marked in extra column (only for the first match, other matches could be ignored).

i have tried an IF function in the for loop like:

FOR v_column_rowA in a..(:v_max_row_columnA) DO

     FOR v_column_rowB in a..(:v_max_row_columnB) DO

               IF(:v_c_columnA[:v_rowA] = v_d_columnB[v_rowB])

               THEN v_c_extracolumn[:v_column_rowA] := mark;

                          v_c_extracolumn[:v_column_rowB] := mark;

i do get data in return but there are no matches to be found. it kinda look like random numbers. Any know how to do this?

Please tell me,Thanks!