In this lesson, we’ll learn how to give columns alias names. It’s very useful when the result of one query is the input for another query. Wait, what?! You can query … another query?! Yes and more! We’ll learn a couple of tricks before combining queries and aliases is the first one.
Let’s look at the
created_at column in the
SELECT id, signup_date, created_at FROM users
We’ve learned that the
created_at column contains the precise timestamp when a user record was created. If we use the
users table in a more complex query naming could get confusing (because the
created_at column could also exist in other tables). To give it a better name we can use alias operator AS:
SELECT id, signup_date, created_at AS signup_timestamp FROM users
If you run this query you’ll see that column name in the result changed from
Another good example is columns produced by aggregate functions:
SELECT COUNT(*) FROM users
This query will produce the result like:
It’s a 1x1 table with a column name count (assigned by default). If later we want to reuse it, it’s better to refer to it as users_count or even better total_users_count:
SELECT COUNT(*) AS total_users_count FROM users
1 step closer to write even more complex queries! Now go and practice these
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 (you’re looking at one atm) and exercises. They always have a real-life setting and detailed explanations. You can immediately apply everything you’ve learned at work.