Joe Celko

Joe Celko is one of the most widely read of all writers about SQL, and was the winner of the DBMS Magazine Reader's Choice Award four consecutive years. He is an independent consultant living in Austin, TX. He has taught SQL in the US, UK, the Nordic countries, South America and Africa.
He served 10 years on ANSI/ISO SQL Standards Committee and contributed to the SQL-89 and SQL-92 Standards.
He has written over 800 columns in the computer trade and academic press, mostly dealing with data and databases. He is the author of eight books on SQL for Morgan-Kaufmann, including the best selling SQL FOR SMARTIES.
Joe is a well-known figure on Newsgroups and Forums, and he is famous for his his dry wit. He is also interested in Science Fiction.

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11 April 2016
11 April 2016

The Practical Problems of Determining Equality and Equivalence in SQL

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In theory, it is easy to determine whether data is equal to, greater than or lesser than a value. Real-world data types can be surprisingly tricky, even for gauging data equivalence. Because SQL cannot remain aloof from any application's data types, you need to be aware of the ways and pitfalls of individual datatypes and how you can test for equality, equivalence, similarity, identity and all that jazz… Read more
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15 December 2015
15 December 2015

Declarative SQL: Using References

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There are several ingenious ways of using SQL References to enforce integrity declaratively. Declarative Referential Integrity (DRI) is more effective than using procedural code in triggers, procedures or application layers because it uses the SQL paradigm, thereby making optimisation easier and providing clearer expression of the rules underlying the data.… Read more
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04 December 2015
04 December 2015

Declarative SQL: Using UNIQUE Constraints

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In SQL, you can express the logic of what you want to accomplish without spelling out the details of how the database should do it. Nowhere is this more powerful than in constraints. SQL is declarative, and Joe Celko demonstrates, in his introduction to Declarative SQL, how you can write portable code that performs well and executes some complex logic, merely by creating unique constraints.… Read more
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14 July 2015
14 July 2015

SQL Style Habits: Attack of the Skeuomorphs

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Although we like to think that our programming techniques are progressive and in tune with the bleeding edge of software development practices, too often they are directly influenced by restrictions faced in the post-war decades when computers first became mainstream. As these restrictions no longer apply, is it time to relinquish such things as cursors, 'tibbling', storing display formats, using short names for symbols and primary keys?… Read more
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11 February 2015
11 February 2015

The DRI Subject of References

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A database must be able to maintain and enforce the business rules and relationships in data in order to maintain the data model. It does this through referential constraints. They aren't complex, but are powerful, especially with the means to attach DRI actions to them. Joe Celko explains all, and pines for the ANSI CREATE ASSERTION statement… Read more
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17 October 2014
17 October 2014

Data Is Crazier than You Think

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As a society, we have an unrealistic respect for data, especially if it has a decimal point somewhere and uses metric units. We who are in the business of data need to cultivate a renewed interest in the sceptical and rigorous science of statistics: it is too important to leave to 'Data Scientists'. If the data is wrong, or the way we analyse or report it is misleading, much of what we do is pointless… Read more
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05 June 2014
05 June 2014

The SQL of The Game of Life

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Joe finds a reference to Conway's Game of Life whilst clearing out his desk, and is suddenly gripped with nostalgia. It wasn't just flares, mullets and disco, but simple computer games in interpreted basic. Somehow, Conway s Game of Life was too intriguing to be abandoned in the attic. Can it be implemented in SQL? Joe sets up a challenge.… Read more
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06 March 2014
06 March 2014

On Handling Dates in SQL

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The calendar is inherently complex by the very nature of the astronomy that underlies the year, and the conflicting historical conventions. The handling of dates in TSQL is even more complex because, when SQL Server was Sybase, it was forced by the lack of prevailing standards in SQL to create its own ways of processing and formatting dates and times. Joe Celko looks forward to a future when it is possible to write standard SQL date-processing code with SQL Server.… Read more
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