text: # case statements the most exiciting part of logical operation
  
  SELECT title, released_year,
      CASE
          WHEN released_year >= 2000 THEN 'Modern Lit'
          ELSE '20th century lit'
      END AS genre
  FROM books;
  
  SELECT title, stock_quantity,
      CASE 
          WHEN stock_quantity <= 50 THEN '*'
          WHEN stock_quantity > 50 AND stock_quantity <= 100 THEN '**'
          ELSE '***'
      END AS stock
  FROM books;
  
  SELECT CONCAT(author_fname, ' ', author_lname),
      CASE
          WHEN stock_quantity <=50 THEN 'Best Selling'
          WHEN stock_quantity >50 AND stock_quantity <=100 THEN 'Popular'
          ELSE 'Not Bad'
      END AS popularity
  FROM books;
  
  # by using case statement we can manipulate the data we have without adding more data to the database, less space used cheaper database means we can perform much complex logical operation that serve as our business logic