For example, Microsoft's SQL Server has an "Exists" keyword allowing you to easily check to see if a record exists; Oracle's SQL does not have this feature, but you can work around the shortcoming ...

The result of an EXISTS condition is true if the subquery resolves to at least one row. The result of a NOT EXISTS condition is true if the subquery evaluates to zero rows. For example, the following ...

EXISTS, NOT IN, and NOT EXISTS, you can avoid a very common problem when NULLs appear in the data of a subquery. Scott Stephens worked for Oracle for more than 13 years in technical support, e ...

However, aside from situations like this, the issue of whether null values should be used in a database is often debated amongst software developers, and is known as the Null Dilemma.