When writing DDL in SQL, you can specify a couple of constraints on columns, like NOT NULL or DEFAULT constraints. Some people might wonder, if the two constraints are actually redundant, i.e. is it still necessary to specify a NOT NULL constraint, if there is already a DEFAULT clause? The answer is: Yes! Yes, you … Continue reading Have You Ever Wondered About the Difference Between NOT NULL and DEFAULT?
This is something where many hours of debugging have been spent in the lives of many SQL developers. The various situations where you can have NULL values in NOT IN predicates and anti-joins. Here's a typical situation: with data as ( select 1 as id from dual union all select 2 as id from dual … Continue reading SQL incompatibilities: NOT IN and NULL values