mysql> create table nicks ( nick varchar(30) not null default '', primary key (nick));
Query OK, 0 rows affected (0.00 sec)

mysql> insert into nicks values ('snacky');
Query OK, 1 row affected (0.00 sec)

mysql> insert into nicks values ('goober');
Query OK, 1 row affected (0.01 sec)

mysql> insert into nicks values ('plasmo');
Query OK, 1 row affected (0.00 sec)

mysql> insert into nicks values ('ap');
Query OK, 1 row affected (0.00 sec)

mysql> insert into nicks values ('nd');
Query OK, 1 row affected (0.00 sec)

mysql> insert into nicks values ('zillion');
Query OK, 1 row affected (0.00 sec)

mysql> select nick, CASE LENGTH(nick) WHEN LENGTH('plasmo') THEN 'Nick is correct length' ELSE 'Nick is incorrect length' END AS 'Nick Length Evaluation' FROM nicks;
+---------+--------------------------+
| nick    | Nick Length Evaluation   |
+---------+--------------------------+
| ap      | Nick is incorrect length |
| goober  | Nick is correct length   |
| nd      | Nick is incorrect length |
| plasmo  | Nick is correct length   |
| snacky  | Nick is correct length   |
| zillion | Nick is incorrect length |
+---------+--------------------------+

6 rows in set (0.00 sec)