I assume you are talking about either 'plpgsql' or psql. 'plpgsql' is
the name of the analogue of Oracle's pl/sql and psql is the analogue
of SQL*Plus.
In plpgsql, you can drop functions using the syntax:
drop function user_demographic_summary (<parameter types>)
where <parameter types> is a comma separated list of the data types of
the input parameters (if any), such as integer, string, etc. You can
easily get these by looking at the file that defined the function, or
querying the data dictionary.
