Lætitia Avrot is Field CTO for EDB in France. She began working with PostgreSQL in 2007. She also had to learn Oracle and SQL Server at the same time. She had a lot of exciting experiences with high availability, production crashes, disaster recovery plan, load balancing, spatial data... She’s involved with the community as she was elected PostgreSQL Europe treasurer, she co-founded Postgres Women, and she's a recognized PostgreSQL project contributor.
Abstract: Of course, you know everything you need to know about NULL! Well, are you sure?
NULL and three-valued logic are often misunderstood and can induce poorly written queries, wrong written
queries (when the result is not as expected) and a lot of time lost trying to figure
out what your missing colleague wanted to do with such a tricky and bad-twisted
SQL code.
After defining NULL and UNKWON (and you'll see that it's not so simple), we'll
go through different use cases where 3-valued is used, what pit you don't want
to fall into and how you can improve query writing, now that you fully understand
what's behind NULL in PostgreSQL.
Slides