The 3-Minute Test: What do you know about SQL performance?

“SQL-Tuning is black magic 
like alchemy:
it consists of obscure rules,
understood only by a handful
of insiders.”

That is a myth. SQL databases use well-known algorithms to deliver predictable performance. It is, however, easy to write SQL queries that cannot use the most efficient algorithm and thus deliver unexpected performance.

The following questions provide examples that might make you believe that SQL tuning is black magic. The explanations at the end are just a few sentences long and reveal that the black magic is pure science.

Choose your Database

MySQL Oracle PostgreSQL SQL Server  

About the Author

Photo of Markus Winand
Markus Winand tunes developers for high SQL performance. He also published the book SQL Performance Explained and offers in-house training as well as remote coaching at