Syntax:
ALTER
    [ALGORITHM = {UNDEFINED | MERGE | TEMPTABLE}]
    [DEFINER = { user | CURRENT_USER }]
    [SQL SECURITY { DEFINER | INVOKER }]
    VIEW view_name [(column_list)]
    AS select_statement
    [WITH [CASCADED | LOCAL] CHECK OPTION]

This statement changes the definition of a view, which must exist. The
syntax is similar to that for CREATE VIEW and the effect is the same as
for CREATE OR REPLACE VIEW. See [HELP CREATE VIEW]. This statement
requires the CREATE VIEW and DROP privileges for the view, and some
privilege for each column referred to in the SELECT statement.

URL: http://dev.mysql.com/doc/refman/5.0/en/alter-view.html

