Determine if a SQL query alters the database structure

Question

I'm trying to find out if a string contains certain SQL commands that alter the database by:

• creating new tables
• deleting existing tables
• creating new table columns
• deleting existing table columns

Right now I'm doing a strpos search for ALTER, CREATE and DROP which should work.

Are there any other commands that do the things above and that I should include in my search?

Note that I don't need this for security reasons. I just need to know if the table schema changed, so I can update my local cache of the schema info...