mysql> select * from tok1;
+-------+-------+
| token | count |
+-------+-------+
| a     |     1 |
| b     |     2 |
+-------+-------+
2 rows in set (0.00 sec)

mysql> select * from tok2;
+-------+-------+
| token | count |
+-------+-------+
| b     |     1 |
| c     |     4 |
+-------+-------+
2 rows in set (0.00 sec)

mysql>  insert into all_tok select token,count,0 from tok1 union select token,0,count from tok2;
Query OK, 4 rows affected (0.01 sec)
Records: 4  Duplicates: 0  Warnings: 0

mysql> select * from all_tok;
+-------+--------+--------+
| token | count1 | count2 |
+-------+--------+--------+
| a     |      1 |      0 |
| b     |      2 |      0 |
| b     |      0 |      1 |
| c     |      0 |      4 |
+-------+--------+--------+
4 rows in set (0.00 sec)

mysql> select token,sum(count1+count2) from all_tok group by token;
+-------+--------------------+
| token | sum(count1+count2) |
+-------+--------------------+
| a     |                  1 |
| b     |                  3 |
| c     |                  4 |
+-------+--------------------+
3 rows in set (0.00 sec)

mysql>