Delphi Query/Table filters and Oracle

How can I filter the result of a TQuery/Table on an Oracle Database EXACT match filters work, e.g.
username='tom'
WILDCARD filters dont work
username='t*'
or
username='t%'
or
username='t?'

Question : Can filters be used on ORACLE tables ? I can get these working on local tables (NOT Oracle).
Any Ideas ?

Also
What is the difference in filtering the result of a TQuery, e.g nusrname='a*'
and
putting USERNAME LIKE 'a*', in the SQL statement ?

TIA
Mike.

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