REGEXP_SUBSTR( string, pattern [, start_position [, nth_appearance [, match_parameter [, sub_expression ] ] ] ] )

-- library_books : id, title, author, genders, total_views ...

/*

    Library Books

    (1, 'The Great Gatsby 2013', 'F. Scott Fitzgerald', 'Fiction; Drama; Romance', 84)

    (2, '2000 - The year of the demon', 'Sebastian Whatever', 'Fiction; Drama; Mystery', 59)

    (3, '1984', 'George Orwell', 'Fiction; Drama; Science Fiction', 12)

    (4, 'Pride and Prejudice', 'Jane Austen', 'Fiction; Drama; Romance', 6)

    (5, '2103: The Deadly Wake', 'G. Philip Jackson', 'Fiction; Drama; Mystery', 101)

    (6, 'Animal Farm', 'George Orwell', 'Fiction; Drama; Science Fiction', 99)

    (7, 'Cyborg 2087', 'Franklin Adreon', 'Fiction; Thriller', 24)

    (8, '2069: A Sex Odyssey', 'Georg Tressler', 'Fiction; Comedy', 75)

    (9, '3022', 'John Suits', 'Fiction; Mystery', 3)

    (10, 'The Alchemist', 'Paulo Coelho', 'Fiction; Drama; Fantasy', 278)

*/

WITH bk_gender AS

(

    SELECT 

        regexp_substr(genders, '[^;]+', 1, level) AS gender,

        total_views

    FROM 

        library_books

    CONNECT BY 

        regexp_substr(genders, '[^;]+', 1, level) IS NOT NULL

        AND PRIOR genders = genders

        AND PRIOR sys_guid() IS NOT NULL

)

SELECT 

    gender,

    sum(total_views) AS total_views

FROM 

    cats

GROUP BY 

    gender

ORDER BY 

    total_views DESC

-- Another example - Year of the book (Year is on the title)

SELECT

    title,

    TO_NUMBER(REGEXP_SUBSTR(title, '\d{4}')) AS vintage_year

FROM

    library_books

WHERE

    1 = 1

    AND REGEXP_LIKE(title, '\d{4}')