SQL Window functions are an advanced type of function in SQL. In this post, you will learn about what SQL window functions are and how they can be used or work.
What are SQL window functions?
SQL window functions are calculation functions similar to aggregate functions but, unlike normal aggregate functions like “group by,” have access to individual rows and can even add some of their attributes into the result set.
We will discuss the topic under the following subheadings:
- What is an SQL Window Function?
- Types of SQL Window Functions
Some of the window functions
What is an SQL Window Function?
A window is a set of rows or observations in a table or result set. In a table, you may have more than one window depending on how you specify the query. A window is defined using the
OVER() clause in SQL. Functions are predefined in SQL and you use them to perform operations on data. They let you do things like aggregating data, formatting strings, extracting dates, and so on.
So Windows functions are SQL functions that enable us to perform operations on a window – that is, a set of records.
Types of SQL Window Functions
There are a lot of window functions that exist in SQL but they are primarily categorized into 3 different types:
- Aggregate window functions
- Value window functions
- Ranking window functions
Aggregate window functions are used to perform operations on sets of rows in a window(s). They include
COUNT(), and others.
Rank window functions are used to rank rows in a window(s). They include
ROW_NUMBER(), and others.
Value window functions are like aggregate window functions that perform multiple operations in a window, but they’re different from aggregate functions. They include things like
FIRST_VALUE(), and others.
I hope you find this post informative!
Now read: Difference between SQL and MySQL
Why are they called window functions in SQL?
Because they operate over a “window frame” which is a set of rows relative to the current row, which can be specified with more precision using the ROWS or RANGE keyword.
What is window function vs subquery in SQL?
In summary, subqueries and window functions are used for different purposes in SQL, and each has its strengths and weaknesses. Window functions are often more efficient and maintainable for calculations across related rows, while subqueries are useful for filtering and aggregating data based on conditions.