Extended Query: Parse Command: syntax?

When you send the query to be parsed I presume you must somehow tell
which elements of it are parameters.  How do you do this?

e.g.:   SELECT name, phone FROM friends WHERE age > 25;

How would I write this if "name" and "25" must be parameters?  Or if
the operator ">" should be a parameter or modifiable in another way?

(Is there a good tutorial site on the extended query language?  It
seems there's almost no information about this on the net.)

Thanks,

Marc