Distributed SQL is a key feature of YugabyteDB, enabling the use of SQL across multiple nodes in a distributed system. YugabyteDB provides several options for optimizing performance in integration testing, including using ramdisk directories, reducing shards per tserver, and setting replication factor to 1. The YSQL equivalent of SQL Server's ISNULL() function is COALESCE(), and duplicate rows can be found using GROUP BY and HAVING clauses, or by using DISTINCT ON to remove them. YugabyteDB also provides new documentation on read replica clusters, JSON data types, and a quickstart page for getting started with the database. Additionally, there are new blogs, tutorials, and videos available on various topics related to YugabyteDB.