10 Cool SQL Optimisations That do not Depend on the Cost Model

Cost Based Optimisation is the de-facto standard way to optimise SQL queries in most modern databases. It is the reason why it is really really hard to implement a complex, hand-written algorithm in a 3GL (third generation programming language) such as Java that outperforms a dynamically calculated database execution plan, that has been generated from … Continue reading 10 Cool SQL Optimisations That do not Depend on the Cost Model

How to Write Efficient TOP N Queries in SQL

A very common type of SQL query is the TOP-N query, where we need the "TOP N" records ordered by some value, possibly per category. In this blog post, we're going to look into a variety of different aspects to this problem, as well as how to solve them with standard and non-standard SQL. These … Continue reading How to Write Efficient TOP N Queries in SQL

JOIN Elimination: An Essential Optimiser Feature for Advanced SQL Usage

The SQL language has one great advantage over procedural, object oriented, and "ordinary" functional programming languages. The fact that it is truly declarative (i.e. a 4GL / fourth generation programming language) means that a sophisticated optimiser can easily transform one SQL expression into another, equivalent SQL expression, which might be faster to execute. How does … Continue reading JOIN Elimination: An Essential Optimiser Feature for Advanced SQL Usage