mysql> explain SongCode;
+------------------+--------------+------+-----+---------+----------------+
| Field            | Type         | Null | Key | Default | Extra          |
+------------------+--------------+------+-----+---------+----------------+
| emailId          | bigint(20)   | NO   | MUL | NULL    |                |
| occVersionNumber | int(11)      | NO   |     | NULL    |                |
| code             | varchar(128) | NO   |     | NULL    |                |
| id               | bigint(20)   | NO   | PRI | NULL    | auto_increment |
+------------------+--------------+------+-----+---------+----------------+
4 rows in set (0.00 sec)

mysql> explain EmailRecord;
+------------------+--------------+------+-----+---------+----------------+
| Field            | Type         | Null | Key | Default | Extra          |
+------------------+--------------+------+-----+---------+----------------+
| occVersionNumber | int(11)      | NO   |     | NULL    |                |
| email            | varchar(128) | NO   | UNI | NULL    |                |
| id               | bigint(20)   | NO   | PRI | NULL    | auto_increment |
| useCount         | bigint(20)   | NO   |     | NULL    |                |
+------------------+--------------+------+-----+---------+----------------+
4 rows in set (0.00 sec)