This guide serves as the definitive reference for understanding the KeySQL query language. If you are familiar with the SQL language that manages data held in relational database management systems (RDBMS), then you are already familiar with KeySQL. KeySQL was invented to readily manage all enterprise data, including the fast-growing volumes of non-flat data native to the likes of JSON and XML. It adheres to the SQL standard of productivity while dealing with data structures much more complex than relational tables. And it makes the powerful RDBMS functionality including joins, set operations, and aggregations, equally applicable to the non-flat data.