SQL first appeared in 1974 as SEQUEL, a query language designed by Donald Chamberlin and Raymond Boyce at IBM's San Jose Research Laboratory. Understanding how IBM's SEQUEL became the SQL language means going back to Edgar F. Codd, a fellow IBM researcher whose 1970 paper "A Relational Model of Data for Large Shared Data Banks" proposed storing data as tables and querying it with mathematics rather than pointer navigation. SQL is the language that turned Codd's theory into something programmers and analysts could type.
How IBM's SEQUEL became the SQL language
Codd's own query language, Alpha, was based on predicate calculus and hard for non-mathematicians to read. Chamberlin and Boyce first designed SQUARE, which used a subscript notation, and then SEQUEL, the Structured English Query Language, which read more like English: SELECT, FROM, WHERE. Their paper appeared in 1974. Boyce died in 1974 at just 26, shortly after it was published.
IBM built System R in the mid-1970s as a research prototype to prove that a relational database could perform well. SEQUEL was its query language. Because "SEQUEL" was a trademark of the British aircraft company Hawker Siddeley, IBM shortened the name to SQL. That is why people still argue over pronouncing it "sequel" or "S-Q-L". Both are fine.
IBM was slow to ship. A small company called Relational Software, Inc., founded by Larry Ellison, Bob Miner and Ed Oates, read the System R papers and released Oracle Version 2 in 1979, generally cited as the first commercial SQL database. IBM followed with SQL/DS in 1981 and DB2 in 1983.
Standards from SQL-86 to SQL:2023
ANSI adopted SQL as a standard in 1986, and ISO followed in 1987. The standard has grown a great deal since.
| Standard | Notable additions |
|---|---|
| SQL-86/87 | First ANSI and ISO standard |
| SQL-92 | Explicit JOIN syntax, more data types, large revision |
| SQL:1999 | Recursive queries (WITH RECURSIVE), triggers, user-defined types |
| SQL:2003 | Window functions, XML support, MERGE |
| SQL:2011 | Temporal (system-versioned) tables |
| SQL:2016 | JSON functions, row pattern recognition |
| SQL:2023 | Property graph queries (SQL/PGQ), JSON data type |
No major database implements the entire standard, and every vendor adds its own extensions. PostgreSQL is usually considered the closest to the standard among popular systems.
Design and key features
SQL is declarative: you describe the result you want and the database's query optimizer decides how to get it. That separation is the core of its success. A query written in 1990 can run faster today simply because optimizers and storage engines improved.
- DDL (data definition):
CREATE TABLE,ALTER,DROP. - DML (data manipulation):
SELECT,INSERT,UPDATE,DELETE. - DCL and transactions:
GRANT,COMMIT,ROLLBACK. - Set-based thinking: operations apply to whole sets of rows, not one record at a time.
- Three-valued logic with
NULL, a frequent source of surprises.
SELECT d.name,
COUNT(*) AS staff,
AVG(e.salary) AS avg_salary
FROM employees e
JOIN departments d ON d.id = e.dept_id
WHERE e.hired >= DATE '2020-01-01'
GROUP BY d.name
HAVING COUNT(*) > 5
ORDER BY avg_salary DESC;The written order (SELECT first) differs from the logical order of evaluation (FROM, WHERE, GROUP BY, HAVING, SELECT, ORDER BY). Knowing that explains why an alias defined in SELECT often cannot be used in WHERE.
Where SQL is used
Practically everywhere data is stored: Oracle Database, IBM Db2, Microsoft SQL Server, PostgreSQL, MySQL, MariaDB and SQLite, which ships inside every Android and iOS device. Analytical engines such as Snowflake, BigQuery, DuckDB, Apache Spark SQL and Trino speak SQL dialects too. Procedural extensions add loops and variables: Oracle's PL/SQL, Microsoft's Transact-SQL and PostgreSQL's PL/pgSQL.
Influence and legacy
Codd received the Turing Award in 1981. SQL's influence shows in query languages for other data models, from SPARQL for RDF and Cassandra's CQL to Microsoft's LINQ and the ISO graph query language GQL, published in 2024. The NoSQL movement of the late 2000s set out to replace SQL, and many of those systems later added SQL-like interfaces anyway.
Is SQL still used today?
More than ever. It is one of the most requested skills in developer and data analyst job listings, and new databases almost always ship with a SQL layer. The arc of how IBM's SEQUEL became the SQL language, from a research prototype to a standard spoken by every major database, shows how a well-chosen abstraction can outlive the hardware and companies that created it.
Frequently asked questions
Why was SEQUEL renamed to SQL?
"SEQUEL" was already a trademark held by the UK aircraft maker Hawker Siddeley. IBM dropped the vowels and used SQL instead. The original pronunciation survived, which is why many people still say "sequel".
Was Oracle really the first commercial SQL database?
Oracle Version 2, released by Relational Software in 1979, is commonly cited as the first commercially available SQL relational database. There was no "Version 1"; the number was chosen to make the product sound mature. IBM's own SQL products arrived in the early 1980s.
Is SQL a programming language or just a query language?
Standard SQL began as a query language, but since SQL:1999 added recursive queries it has been Turing complete. In practice, procedural dialects like PL/SQL and T-SQL are used to write full programs inside the database, while plain SQL stays focused on describing data.
