Learn about EXISTS ( you need to know it so you can do an update/insert statement in the same pass anyway ) On MSSQL/Sybase I would do something like:

IF EXISTS ( SELECT 1 FROM sysobjects where name = 'some_table' and typ
+e = 'U' )
-- do this if true ( maybe an update here )
SELECT 1
ELSE
-- do this if false ( maybe an insert here )
SELECT 0
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You need to consult the docs as to how your database implements EXISTS which normally operates on a subquery and returns a boolean.
JamesNC