CREATE FUNCTION TABLE_EXISTS(p_strTableName varchar(30))
  RETURNS BOOLEAN 
AS
BEGIN
  RETURN
    EXISTS
    (
      SELECT
        NULL
      FROM RDB$RELATIONS R
      WHERE
        R.RDB$RELATION_NAME = p_strTableName AND
        R.RDB$SYSTEM_FLAG=0 AND
        R.RDB$RELATION_TYPE=0
    );
END;