MariaDB/MySQL IS NULL conditions and indexes
It is not uncommon for an application to use WHERE conditions like this: WHERE status = ‘DELETED’ OR status IS NULL If you run EXPLAIN, such conditions typically only cause the type column to be show ref_or_null. Whereas,...
When to use NULLable columns in relational databases
In the article What does NULL mean in SQL? I explained why I consider SQL NULL inconsistent. As a general rule, I should have made clear that I don’t think it is a good idea to use NULL, even if columns are NULLable by default in SQL....
What does NULL mean in SQL?
There have been endless discussions already if NULL should be implemented in relational databases, and if it should even be included in the relational theory. My favourite quote on this subject is from the person who helped Ted Codd to divulgate – and probably refine...
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