What is Entity SQL? Why introduce a new query language (eSQL); why not use SQL?
SQL is the time proven query language for data access. However, since EDM introduces an enhanced data model which builds on entities, rich types and relationships, we need a query language that enables programmers to reason, express and write queries in terms of EDM abstractions. EntitySQL was designed to address this need. Among the many requirements, it is worth to call out some driving aspects of the language design: Types: Support EDM types in a clean and expressive way; SQL based: Provide a natural transition for SQL developers. While EntitySQL was heavily influenced by SQL, EntitySQL is not pure SQL. It is worth mentioning that EntitySQL does not prevent one from writing classic SQL queries, users can navigate relationships using classic joins/foreign-keys. EntitySQL also supports relationships to simplify this common task. Composable and orthogonal: In some SQL implementations, certain expressions can only be placed in specific constructs.
