gistfile1.txt

mysql> select * from german;
+----+-------+
| id | word  |
+----+-------+
|  1 | hallo |
|  2 | welt  |
+----+-------+
2 rows in set (0.00 sec)

mysql> select * from english;
+----+-------+
| id | word  |
+----+-------+
|  1 | hello |
|  2 | world |
+----+-------+
2 rows in set (0.00 sec)

mysql> select german.word, english.word from german, english;
+-------+-------+
| word  | word  |
+-------+-------+
| hallo | hello |
| welt  | hello |
| hallo | world |
| welt  | world |
+-------+-------+
4 rows in set (0.00 sec)

mysql> select german.word, english.word from german, english where id=id;
ERROR 1052 (23000): Column 'id' in where clause is ambiguous
mysql> select german.word, english.word from german, english where german.id=english.id;
+-------+-------+
| word  | word  |
+-------+-------+
| hallo | hello |
| welt  | world |
+-------+-------+
2 rows in set (0.00 sec)