clauses IN and EXISTS are interchangeable. However, they’re quite different in how they handle NULL values and may give different results. The problem comes from the fact that, in an Oracle database, ...

Null or nonexistent data gets complicated when the application expects a data value and gets nothing or unexpected values; that's when you must perform coding that properly handles these situations to ...

You can define data fields to not store null data by specifying the NU option in data definition statements. In normal data storage (that is, NU not specified), a null value is represented by two ...