One of the trickiest aspects of relational database management can be dealing with missing information. The standard method of representing missing information is to set the “value” to null. A null ...

In database applications, a null object is a valid value for a field. This class differentiates between a null value (a null object) and an uninitialised value (the DBNull.Value instance).

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, a NULL value means unknown ...

while “Y” is the value in four rows, and one row is null. If a query seeks the number of rows where a value of “X” appears, the answer will be five. But for a query asking how many rows exist where a ...