What Is SQL?

What Is SQL?

SQL stands for Structured Query Language.

It is usually pronounced “S-Q-L.”

The director’s instruction sheet

If you came from the DBMS article, you may groan, “This metaphor again?” Bear with me.

Say a TV station is making a program of past footage.

The director hands the editor an instruction sheet: “Only this athlete, only this event.”

The sheet has a set format.

The set format for instruction sheets handed to the DBMS (the editor). That is SQL.

Director (person, app)
     |  instruction sheet (SQL)
     v
Editor (DBMS)
     |  find, store, fix, delete
     v
Archive (data)

SQL is the language for writing requests to a DBMS.

Reading an instruction sheet

Take the clip list from the relational database article.

Clip	Content	Athlete
5001	Final	101
5002	Semifinal	102
5003	Qualifier	101

A sheet asking for “the content of clips with athlete 101” looks like this.

SELECT content
FROM clips
WHERE athlete = 101
ORDER BY clip;

• SELECT: what to take out (content)
• FROM: from which table (clips)
• WHERE: under what condition (athlete is 101)
• ORDER BY: how to sort (by clip number)

Two results come back: “Final” and “Qualifier”.

It lines up what, from where, under what condition, and in what order, close to an English sentence.

The point: you just write what you want.

Four basic requests

Matching the DBMS’s jobs, SQL has four basic words.

SQL word	Request	At a TV station
SELECT	Take out	Find footage and hand it over
INSERT	Put away	Add new footage to the archive
UPDATE	Fix	Rewrite a clip’s details
DELETE	Delete	Remove footage from the archive

Putting away, fixing, and deleting are written in the same set format (PostgreSQL, “Data Manipulation”).

Following numbers to link tables

The clip list has no athlete names. It only has athlete numbers.

The names are in another table, the athlete list.

SELECT clips.content, athletes.name
FROM clips
JOIN athletes
  ON clips.athlete = athletes.athlete;

JOIN links two tables by number into one answer (PostgreSQL, “Joins Between Tables”).

Results come back with names, like “Final Sato,” “Semifinal Suzuki,” and “Qualifier Sato.”

This is how tables can be joined!

Nearly the same words for any DBMS

SQL is an international standard, formally named ISO/IEC 9075 (PostgreSQL, “SQL Conformance”).

Because of the standard, the basic way of writing is shared by PostgreSQL and other DBMSs.

Small details do differ from one DBMS to another.

One more thing: instruction sheets need protecting. Slipping malicious commands in through an input field is called SQL injection (OWASP, “SQL Injection”).

Countermeasures are covered in the DBMS article.

Takeaways

Finally, SQL.

The format is strict, but write only what you want and it works out how to find it.

Subqueries, CTEs, UNION.

It goes pretty deep.

If you can write it fluently, that’s cool 👍

Not me...

Trivia

• SELECT: The SQL word for taking data out.
• JOIN: The SQL word for linking two tables by number.
• ISO/IEC 9075: The formal name of the international SQL standard.
• SQL injection: An attack that slips malicious commands in through an input field.
• System R: An IBM prototype of a table-based database from the 1970s.

History

The beginning: asking without knowing where things are

In 1970, Edgar Codd of IBM published the idea of holding data in tables (Codd, “A Relational Model of Data for Large Shared Data Banks”).

Codd believed users should be able to work closer to natural language, without worrying about where data was stored (IBM, “The relational database”).

Walls and turning points: turning an idea into usable words

Many doubted the idea, so from 1973 IBM tested it in practice with System R (IBM, “The relational database”).

That is where Donald Chamberlin and Raymond Boyce created SQL (IBM, “The relational database”).

In 1977, the company that became Oracle released the first commercial relational database. IBM shipped DB2 in 1983 (IBM, “The relational database”).

SQL later became an international standard and kept being revised (PostgreSQL, “SQL Conformance”).

Different companies, the same words for asking.

What is in development now

• In 2023, the latest version of the standard, ISO/IEC 9075:2023 (SQL:2023), came out (PostgreSQL, “SQL Conformance”).
• In October 2026, the first release candidate of PostgreSQL 19 came out (PostgreSQL, October 15, 2026).

What comes next

Ways to have AI translate natural-language questions into SQL are also being introduced (Microsoft Learn, “Develop intelligent applications with AI frameworks”).

Fifty years on, things are getting closer to the “near natural language” Codd aimed for.

Whether people will stop writing SQL themselves is still unknown.