The core principle governing Structured Query Language (SQL) Dialects is the existence of standardized syntactic subsets derived from ANSI/ISO SQL that diverge through specific extensions to optimize for distinct vendor architectures, data models, and concurrency protocols. Formally defined by adherence to a base grammar with optional clauses like window functions or recursive common table expressions, these dialects constitute subfields within relational database theory rather than interchangeable implementations. Their theoretical significance lies in the trade-off between universal standardization and performance-specific optimization inherent to distributed versus monolithic data processing environments.
This article compares PostgreSQL and MySQL, and in doing so shows what a SQL dialect is: a shared standard core plus each vendor's own additions and relaxations. It lines up the syntax that differs b…