SQL Structured Query Language
Standard language for relational databases. Don Chamberlin + Raymond Boyce, IBM, 1974 — back then called SEQUEL. ANSI standard since 1986.
Built on Edgar Codd's relational algebra (1970). Declarative: describe what you want, the optimizer figures out how. Latest standard: SQL:2023. Dialects: PostgreSQL, MySQL, Oracle, SQL Server, SQLite — all with their own quirks. Reform movements have tried to replace it: NoSQL wave (2009–2015) has faded. NewSQL (CockroachDB, Spanner) brought distributed SQL. Modern AI trend: text-to-SQL via LLM.