Reducing the number of requests to the database using sequences

In this recipe, we continue to explore ways to reduce the number of requests made to the database, illustrating how the use of sequences can help us in achieving this as well as improved database scalability.

Sequences are used to assign a sequential number—unique until the sequence is recreated or reinitialized. In many non-Oracle databases, there are tools that allow developers to automatically assign a sequential number to a field—often the primary key—the so-called autoinc fields (Microsoft® SQL Server® and IBM® DB2® can define a field IDENTITY, MySQL™ has the AUTO_INCREMENT attribute, and so on).

Oracle database doesn't have a specific IDENTITY field, to achieve the same result developers have to write a trigger for the table to assign a value to the "autoinc" field, using a sequence. This behavior, however, allows developers to implement whatever policy they want while generating the autoinc field. Sequences can also be...