ASP+SQL中，UPDATE语法出错解决思路

ASP+SQL中，UPDATE语法出错
conn.execute( "update   bbs,student   set   bbs.cla_id= "&cla_id& "   where   bbs.buser=student.suser   and   student.sid= "&request( "id ")& " ")


错误类型：
Microsoft   OLE   DB   Provider   for   ODBC   Drivers   (0x80040E14)
[Microsoft][ODBC   SQL   Server   Driver][SQL   Server]第   1   行:   ', '   附近有语法错误。

应该怎么改.

谢谢

------解决方案--------------------
conn.execute( "update bbs set cla_id= "&cla_id& " from student where bbs.buser=student.suser and student.sid= "&request( "id ")& " ")