In this post, you will find detailed information on Why are they called window functions?, Why is it called a window function?, What is the window function?

## Why are they called window functions?

Window functions in SQL are named after mathematical functions called “window functions” or “window functions”. These functions operate on a subset or “window” of rows from a query’s result set, rather than aggregating the result set as a whole.

They are designed to perform calculations that require access to multiple rows of the result set simultaneously, enabling operations such as ranking, aggregation, and cumulative calculations. The term “window” in this context refers to the subset of rows on which the function operates, similar to a moving or fixed-size data window in the data set.

### Why is it called a window function?

The term “window function” is used because these functions apply operations on a specified window or subset of rows from a query’s result set.

This window can be set based on various criteria such as partitioning by specific columns, ordering within the partition, and framing (specifying the row range) relative to the current row.

By specifying the window, SQL developers can control which rows are included in the function’s result calculation, allowing for more sophisticated and flexible data analysis compared to traditional aggregate functions.

### What is the window function?

A window function in SQL refers to a type of function that performs a calculation on a set of rows related to the current row in a query result set.

Unlike aggregate functions like SUM() or AVG(), which calculate a single result from a group of rows, window functions operate on a window of rows defined by a partition and an optional command specification. Common examples include rank functions (rank(), dense_rank()), aggregate functions on Windows (SUM(), AVG()), and cumulative distribution functions (CUME_DIST()).

These functions provide powerful capabilities for analytical queries, enabling complex calculations and comparisons between different rows in the same query result.

Window functions are used in SQL to perform complex analytical tasks that are difficult or inefficient to perform using standard aggregate functions or subquestions. They provide a way to calculate values based on a subset of rows in the result set, without the need for auto-jins or temporary tables.

SQL developers use window functions to generate rankings, calculate moving averages, calculate running totals, and compare data points across different partitions or sets of ordered rows. By leveraging window functions, SQL queries can efficiently perform advanced analytical operations and produce insightful reports or summaries from large data sets.

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