SQL Window Functions: A Practical Guide

Mon, 06 Apr 2026 00:00:00 +0000

Window functions are one of the most powerful and underused features in SQL. Unlike GROUP BY, they let you perform calculations across a set of rows related to the current row — without collapsing the result set.

The Core Syntax

function_name() OVER (
 PARTITION BY column1
 ORDER BY column2
 ROWS/RANGE BETWEEN ... AND ...
)

Clause	Purpose	Required?
`PARTITION BY`	Divides rows into groups (like GROUP BY, but rows are kept)	No
`ORDER BY`	Defines the order within each partition	Depends on function
Frame (`ROWS BETWEEN`)	Defines which rows to include relative to the current row	No

1. Ranking Functions

`ROW_NUMBER()`

Assigns a unique sequential integer to each row within a partition. No ties.

SQL on DataSubway

SQL Window Functions: A Practical Guide

The Core Syntax

1. Ranking Functions

ROW_NUMBER()

`ROW_NUMBER()`