For example:           SELECT EXTRACT(YEAR FROM DUE_DATE)
                         FROM ACCOUNTS_PAYABLE_TBL;

                       SELECT EXTRACT(YEAR FROM DUE_DATE)
                         FROM ACCOUNTS_PAYABLE_TBL
                        WHERE EXTRACT(YEAR FROM DUE_DATE) = 2051;

                                       or

                       SELECT EXTRACT(YEAR FROM DUE_DATE)
                         FROM ACCOUNTS_PAYABLE_TBL
                       HAVING EXTRACT(YEAR FROM DUE_DATE) = 2051;

The results of scalar functions do not have headings in the result table because they are not existing and unmodified columns in the base table. A scalar argument can be a column name, a column function, or another scalar function.

NULL values that are used in a scalar function will result in a NULL value. If actual values are to be returned, then the column must be defined as NOT NULL WITH DEFAULT so that a default of zero or spaces will be used in the scalar function or a VALUE scalar function may also be used for this purpose.