01Overview

In 1974 Chamberlin and Boyce proposed SEQUEL at IBM, later renamed SQL. It rests on relational algebra but expresses joins, filters and aggregates in a syntax close to English. ANSI standardised it in 1986, and it has been the most durable interface in data ever since.

SQL’s success is its declarativeness: users need not think about indexes or execution order, the optimiser chooses the plan. That same success made it a language of many dialects — window functions, CTEs, JSON and vector search keep being added. Today, from embedded databases to data warehouses, SQL remains the common tongue of data analysis.

02History

  1. 1974

    SEQUEL is proposed

    IBM's relational query language.

  2. 1979

    Oracle ships SQL

    Commercial adoption spreads.

  3. 1986

    SQL-86

    Standardised by ANSI.

  4. 1992

    SQL-92

    One of the most important revisions of the standard.

  5. 2003

    Window functions

    Analytical queries get stronger.

03Core concepts

Declarative query

Describe the result without prescribing the procedure.

Join

Combine several tables on a condition.

Query plan

The execution strategy the optimiser picks, such as an index scan or a hash join.

04Hands-on

Do it once — it beats reading it ten times

Write the same query three ways (join, subquery, window function) and compare the three query plans

05Self-check

Say it in your own words first, then open the answer. Whatever you cannot explain is what to review next.

Can you explain "Declarative query"?

Describe the result without prescribing the procedure.

Can you explain "Join"?

Combine several tables on a condition.

Can you explain "Query plan"?

The execution strategy the optimiser picks, such as an index scan or a hash join.

What problem did it solve, and why was there nothing better at the time?

Go back to the history section: how was this done before, and what did it cost?

If you had to build it today, how would you break it down?

Use the hands-on task above: write a plan of at most three steps before you start.

06Key people

D

Donald Chamberlin

1944 –

Co-designer of SQL.

R

Raymond Boyce

1947 –

Co-designer of SQL.

07Further reading

  • SQL in a NutshellKevin Kline · 2011
  • Database System ConceptsSilberschatz et al. · 1997