CREATE OR REPLACE FUNCTION number_to_words(num INTEGER) RETURNS TEXT AS $$
DECLARE
    units TEXT[] := ARRAY['', 'one', 'two', 'three', 'four', 'five', 'six', 'seven', 'eight', 'nine'];
    teens TEXT[] := ARRAY['eleven', 'twelve', 'thirteen', 'fourteen', 'fifteen', 'sixteen', 'seventeen', 'eighteen', 'nineteen'];
    tens TEXT[] := ARRAY['', 'ten', 'twenty', 'thirty', 'forty', 'fifty', 'sixty', 'seventy', 'eighty', 'ninety'];
    thousands TEXT[] := ARRAY['', 'thousand', 'million', 'billion'];
    num_text TEXT := '';
    temp_num INTEGER;
    segment INTEGER;
    segment_text TEXT;
    index INTEGER := 0;
BEGIN
    IF num = 0 THEN
        RETURN 'zero';
    END IF;

    IF num < 0 THEN
        RETURN 'negative ' || number_to_words(ABS(num));
    END IF;

    WHILE num > 0 LOOP
        segment := num % 1000;
        num := num / 1000;

        IF segment > 0 THEN
            segment_text := '';
            
            -- Handle hundreds place
            IF segment >= 100 THEN
                segment_text := units[segment / 100] || ' hundred ';
                segment := segment % 100;
            END IF;
            
            -- Handle tens and units place
            IF segment >= 20 THEN
                segment_text := segment_text || tens[segment / 10];
                segment := segment % 10;
                IF segment > 0 THEN
                    segment_text := segment_text || '-' || units[segment];
                END IF;
            ELSIF segment >= 11 AND segment <= 19 THEN
                segment_text := segment_text || teens[segment - 10];
            ELSE
                segment_text := segment_text || units[segment];
            END IF;
            
            -- Add the segment text with its thousand place
            IF index > 0 THEN
                segment_text := segment_text || ' ' || thousands[index];
            END IF;

            num_text := segment_text || ' ' || num_text;
        END IF;

        index := index + 1;
    END LOOP;

    RETURN trim(both ' ' FROM num_text);
END;
$$ LANGUAGE plpgsql;