Citus Blog

Today we continue to explore all the powerful and fun things you can do with SQL. SQL is a very expressive language and when it comes to analyzing your data there isn't a better option. You can see the evidence of SQL's power in all the attempts made by NoSQL databases to recreate the capabilities of SQL. So why not just start with a SQL database that scales? (Like my favorites, Postgres and Citus.)

Today, in the latest post in our 'Fun with SQL' series (earlier blog posts were about recursive CTEs, generate_series, and relocating shards on a Citus database cluster), we're going to look at window functions in PostgreSQL. Window functions are key in various analytic and reporting use cases where you want to compare and contrast data. Window functions allow you to compare values between rows that are somehow related to the current row. Some practical uses of window functions can be:

• Finding the first time all users performed some action
• Finding how much each users bill increased or decreased from the previous month
• Find where all users ranked for some sub-grouping

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