难以理解的SQL查询结果

Question

我正在使用mysql（5.1.71）并且在桌子下面。

mysql> DESCRIBE test;
+-------+-------------+------+-----+---------+-------+
| Field | Type        | Null | Key | Default | Extra |
+-------+-------------+------+-----+---------+-------+
| foo   | varchar(30) | YES  |     | NULL    |       |
| hoge  | varchar(30) | YES  |     | NULL    |       |
+-------+-------------+------+-----+---------+-------+
2 rows in set (0.00 sec)

mysql> SELECT * FROM test;
+------+------+
| foo  | hoge |
+------+------+
| aaa  | 111  |
| bbb  | xxx  |
+------+------+
2 rows in set (0.00 sec)

我得到的结果低于查询结果，但为什么它显示第二行？

mysql> SELECT * FROM test WHERE foo=''*'' AND hoge=''*'';
+------+------+
| foo  | hoge |
+------+------+
| bbb  | xxx  |
+------+------+
1 row in set (0.00 sec)

我猜''*''被解释为空字符串的乘法而且查询与SELECT * FROM test WHERE foo=0 AND hoge=0;相同，但我仍然无法理解。