ERROR 1193 (HY000): Unknown system variable (2 replies)

Another one makes me scratch my head. I'm trying to update my database using a prepared statement. I got an java.sql.SQLException: Unknown system variable 'projectnumber'. I tried to execute the SQL statement in my 'MySQL Console' with the same result.

The error states the system variable 'projectnumber' is unknown. But it is a field name. Or am I looking in the wrong direction?

mysql> SET projectnumber=100101, project=TimeKeeper, activity=DAOTest,  per_numb
er=100101, day=2015-04-10, worked_time=04:15:00 FROM projects WHERE pro_id=2;
ERROR 1193 (HY000): Unknown system variable 'projectnumber'
mysql>
mysql>
mysql> describe projects;
+---------------+-------------+------+-----+---------+----------------+
| Field         | Type        | Null | Key | Default | Extra          |
+---------------+-------------+------+-----+---------+----------------+
| pro_id        | int(11)     | NO   | PRI | NULL    | auto_increment |
| projectnumber | varchar(64) | YES  |     | NULL    |                |
| project       | varchar(64) | YES  |     | NULL    |                |
| activity      | varchar(64) | YES  |     | NULL    |                |
| per_number    | varchar(64) | YES  |     | NULL    |                |
| day           | date        | YES  |     | NULL    |                |
| worked_time   | time        | YES  |     | NULL    |                |
+---------------+-------------+------+-----+---------+----------------+
7 rows in set (0.06 sec)