Convert the given numbers into words in Pl/SQL

Prerequisite – PL/SQL introduction
In PL/SQL code groups of commands are arranged within a block. A block group related declarations or statements. In declare part, we declare variables and between begin and end part, we perform the operations.

Given a number and task is to convert each digit of the number into words.
Examples:

Input: 47856
Output: Four Seven Eight Five Six

Input: 123456
Output: one two three four five six

Approach is to select the corresponding word of a particular number using decode function.
Below is the required implementation:

DECLARE

    -- declare variable are num, num_to_word, str, len, c
    -- and in above declare variable num, len, c are integer datatype
    -- and num_to_word and str are varchar datatype
    num         INTEGER;
    num_to_word VARCHAR2(100);
    str         VARCHAR2(100);
    len         INTEGER;
    c           INTEGER;
BEGIN
    num := 123456;

    len := Length(num);

    dbms_output.Put_line('Entered Number is: '
                         ||num);

    FOR i IN 1..len LOOP
        c := Substr(num, i, 1);

        SELECT Decode(c, 0, 'Zero ',
                         1, 'One ',
                         2, 'Two ',
                         3, 'Three ',
                         4, 'Four ',
                         5, 'Five ',
                         6, 'Six ',
                         7, 'Seven ',
                         8, 'Eight ',
                         9, 'Nine ')
        INTO   str
        FROM   dual;

        num_to_word := num_to_word
                       ||str;
    END LOOP;

    dbms_output.Put_line('Number to words: '
                         ||num_to_word);
END;

-- Program End

Output :

Entered Number is: 123456
Number to words: One Two Three Four Five Six