2 October 2026
Meet DIREC researcher, Song Wu
There’s a lot of attention right now on AI’s appetite for energy – data centres competing with local communities for electricity and water. But there’s another layer of that story that gets far less scrutiny: the software running underneath it all. Every time you check out on a shopping site, search for something, or open an app, there’s a database query happening behind the scenes – and each one costs electricity. As Denmark’s digitalization deepens, postdoc researcher Song Wu is working to give that cost the same attention as the flashier AI debate.
Song’s whole academic career – with a bachelor’s and master’s in China, a joint PhD split between Brussels and Aalborg – was related to databases. Speed was always the metric that mattered.
The GreenSQL project takes a different path:
“In the past decades, the main focus of database research has been to make query processing faster. GreenSQL is a completely different direction – we’re extending from runtime-centric research towards energy awareness. It’s a completely new dimension,” says Song.
A query is simply a request you send to a database – a short set of instructions asking it to find, sort, update, or combine pieces of data. Searching for a product, logging into an app, or checking a bank balance all trigger one or more queries behind the scenes, usually written in SQL, the language used by the vast majority of the world’s databases. Each of those queries runs on a server, and that server draws power to execute it – the better or worse the query is written, the more or less electricity it takes to get the same answer.
Companies running millions of database queries a day are already thinking hard about performance – GreenSQL aims to give them the same ability to predict and optimize for energy cost.
“We aim to present a catalogue of energy-efficient query patterns, so businesses can still run with lower consumption and lower environmental impact.”
DIREC’s GreenSQL project is a collaboration across Aalborg University, Roskilde University, and the international software company Software Improvement Group (SIG)
