Window Function

Advanced

Performs calculations across a set of rows related to the current row without collapsing groups.

Syntax

function() OVER (PARTITION BY col ORDER BY col)

Example

SELECT name, department, salary,
  RANK() OVER (PARTITION BY department ORDER BY salary DESC) as dept_rank,
  SUM(salary) OVER (PARTITION BY department) as dept_total
FROM employees;

About SQL Window Function

The Window Function keyword belongs to the Advanced category of SQL statements. Performs calculations across a set of rows related to the current row without collapsing groups. Understanding this command is essential for any developer working with relational databases like PostgreSQL, MySQL, SQLite, or SQL Server.

SQL (Structured Query Language) is the standard language for managing and querying relational databases. The Window Function statement is supported across all major database systems, though specific syntax may vary slightly between PostgreSQL, MySQL, MariaDB, Oracle, SQL Server, and SQLite. Always consult your database's documentation for vendor-specific features and limitations.

Best practices for using Window Function: always test queries on a development database before running them in production, use parameterized queries to prevent SQL injection, and leverage EXPLAIN to understand query performance. For complex queries, consider using CTEs (Common Table Expressions) to improve readability and maintainability.

Related SQL Keywords

OVER PARTITION BY ROW_NUMBER RANK