Syntax:
SET variable_assignment [, variable_assignment] ...

variable_assignment:
      user_var_name = expr
    | [GLOBAL | SESSION] system_var_name = expr
    | [@@global. | @@session. | @@]system_var_name = expr

The SET statement assigns values to different types of variables that
affect the operation of the server or your client. Older versions of
MySQL employed SET OPTION, but this syntax is deprecated in favor of
SET without OPTION.

URL: http://dev.mysql.com/doc/refman/5.5/en/set-statement.html

