Couchbase 6.5 introduces support for window functions, as defined by the SQL:2003 standard, in its Analytics service, enhancing its capability for efficient parallel query processing. Window functions allow for more concise and readable SQL queries, eliminating the need for complex self-joins and subqueries, thus improving query performance. This blog post demonstrates the application of window functions by calculating a running total, showcasing their practical benefits over traditional methods such as INNER JOIN. It highlights how Couchbase Analytics can handle complex joins and aggregations that are typically challenging in NoSQL environments, differentiating it from other NoSQL vendors like Cassandra and MongoDB. The post also provides guidance on setting up a Couchbase Server 6.5 environment to experiment with these features, emphasizing that window functions are a well-established part of SQL and now extend to document databases with Couchbase's latest release.