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.
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
It is awkward to do 'Graph databases' in SQL to explore the sort of relationships and memberships in social networks because equivalence relations are classes (a set of sets) rather than sets. However one can explore graphs in SQL if the relationship has all three of the mathematical properties needed for an equivalence relationship. … Read more
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
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
The SEQUENCE statement introduced in SQL Server 2012 brings the ANSI SQL 2003 standard method of generating IDs. This is a great relief to database professionals as it solves some problems what are awkward to solve with the IDENTITY property. Joe Celko explains the basics of using a SEQUENCE… Read more
The 'Structured' part of SQL denotes the fact that queries can be nested inside each other in such a way that, wherever you can use a table, you can use a table expression. Such derived tables can provide powerful magic, to which is added CTEs and Lateral Tables. Joe Celko explains.… Read more
SQL's windowing functions are surprisingly versatile, and allow us to cut out all those self-joins and explicit cursors. Joe Celko explains how they are used, and shows a few tricks such as calculating deltas in a time series, and filling in gaps.… Read more
A Dominoes game of Texas 42 inspires Joe to explore unusual uses for check constraints and views. Sometimes, the best way of discovering useful SQL techniques is to tackle the more unusual problems.… Read more
Parts explosions present a classic IT problem. How can one calculate such things as weight or cost of assemblies in SQL? Joe shows how it can be done using nested sets, with not an IDENTITY or GUID in sight..… Read more
It should be easy to model a game of poker in SQL. The problem is, however, that you need to model a permutation from a set of elements. Joe Celko argues that using a group of columns to do this isn't necessarily a violation of 1NF, since a permutation is atomic. Then comes the second problem: how would you sort such a column-base permutation in order? Sorting columns in SQL?… Read more
SQL and Relational Theory, by Chris Date, isn't likely to be a book that SQL's greatest defender, Joe Celko, would agree with. However, following the debates between Date and Celko on the relational purity of SQL has all the fascination of watching Godzilla wrestling King Kong.… Read more
Relational Databases have tables as data structures, not arrays. This makes it tricky and slow to do matrix operations, but it doesn't mean it is impossible to do. Joe gives the Celko Slant on how to go about doing Matrix Math in SQL.… Read more
Following up from his popular article, SQL View Basics, Joe delves into the main uses of views, explains how the WITH CHECK OPTION works, and demonstrates how the INSTEAD OF trigger can be used in those cases where views cannot be updatable.… Read more
SQL Views are essential for the database developer. However, it is common to see them misued, or neglected. Joe Celko tackles an introduction to the subject, but there is something about the topic that makes it likely that even the experienced developer will find out something new from reading it.… Read more
The 'bin packing' problem isn't just a fascination for computer scientists, but comes up in a whole range of real-world applications. It isn't that easy to come up with a practical, set oriented solution in SQL that gives a near-optimal result. … Read more
Voting systems can become very complex, and some of them are easy to manipulate by tactical voting. Joe takes a couple of voting systems and wonders how you would implement them in SQL. He's even more curious as to how you, the reader, would do so. … Read more
Unlike the hierarchical database model, which created a tree structure in which to store data, the network model formed a generalized 'graph' structure that describes the relationships between the nodes. Nowadays, the relational model is used to solve the problems for which the network model was created, but the old 'network' solutions are still being implemented by programmers, even when they are less effective.… Read more
The sequential nature of early data storage devices such as punched card and magnetic tape once forced programmers to devise algorithms that made the best of sequential access. These ways of doing data-processing have become so entrenched that they are still used in modern relational database systems. There is now a better way, as Joe explains.… Read more