The standard language for managing and manipulating a Relational Database.
It is common to use uppercase for SQL commands (e.g., SELECT, JOIN) and lowercase identifiers like table or column names (e.g., users, email) to easier distinguish them.
Dialects
Each Relational Database Management System (RDBMS) implement their own dialect of SQL, but must adhere to a core SQL syntax defined by ISO/IEC 9075.
Common dialects are:
PostgreSQL: known for advanced data types and extensibility.- MySQL: widely used in web development and open-source stacks.
T-SQL (Transact-SQL): Microsoft’s extension for SQL Server, including procedural programming features.PL/SQL (Procedural Language/SQL): Oracle’s extension that adds procedural capabilities like loops and variables.SQLite: lightweight, file-based engine used extensively in mobile apps and embedded systems.