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How to give a query optimizer fits

Recently I have been interacting with a number of people, including Lukas Eder of JOOQ and consultant/blogger Vlad Mihalcea, on SQL and its merit as a query language, particularly with respect to object-relational mapping frameworks such as Hibernate. With native HQL, or with JPA’s JPQL language, Hibernate is responsible for creating the SQL query passed

 
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Why the SQL Standard does not need another way to do GROUP BY

In a recent article, Lukas Eder proposed enhancements to the SQL Standard’s GROUP BY syntax to include support for implicit grouping attributes, such as that provided by the Cypher query language. I applaud Lukas’ efforts to define useful changes to the SQL language, but I am going to try to show in this article that

 
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Set-level operations do matter

A recent email exchange with software consultant Breck Carter regarding the performance of user-defined functions in SQL has prompted me to re-post this article that I originally wrote in 2008. User-defined functions in SQL have their uses; unfortunately their performance characteristics are highly variable because it is very difficult impossible for a query optimizer to

 
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Surrogate identifiers

This semester I’m teaching a course entitled “Application programming with Oracle” and one of the things I want to stress to my students is the interdependency between design decisions and database application performance. Early in the term we are looking at database design tradeoffs, and those discussions reminded me of this blog post from 2008,

 
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The first deadly sin

In this semester I’m teaching two SQL fundamentals courses, one with MySQL and one with Microsoft SQL Server. We are quickly reaching the point where the notions of query equivalence and support for domains will be necessary – and that reminded me of this blog post that I wrote last spring while I was still

 
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