snippet.txt

if Book.exists?(:title => title) # SELECT #=> true/false
  book = Book.find_by_title(title) # SELECT #=> Book
  ...
  
if book = Book.find_by_title(title) # SELECT || nil
  ...


if book = Book.find_by_title(title) && company = Company.find_by_name(name)
  ...  

if book = (Book.find_by_title(title) && company = Company.find_by_name(name))
  # book => (boolean)  
  # company => (<Company>) 

if (book = Book.find_by_title(title)) && (company = Company.find_by_name(name))
  # book => (boolean)  
  # company => (<Company>)