Before we dive deeper into window functions let’s practice what we’ve already learned. 
In this exercise let’s calculate the percentage of all users who signed up via Facebook.
As usual, submit the integer part of the percentage. For example, if it’s 39.71639 submit 39 as the answer.
About SQL Habit
Hi, it’s Anatoli, the author of SQL Habit. 
SQL Habit is a course (or, as some of the students say, “business simulator”). It’s based on a story of a fictional startup called Bindle. You’ll play a role of their Data Analyst 
and solve real-life challenges from Business, Marketing, and Product Management.
SQL Habit course is made of bite-sized lessons and exercises (you’re looking at one atm). They always have a real-life setting and detailed explanations. You can immediately apply everything you’ve learned at work. 
