Benefits of Using a Relational Database
RDBMSs offer various benefits by controlling the following:
• Redundancy: RDBMSs prevent having multiple duplicate copies of the same data,which takes up disk space unnecessarily.
• Inconsistency: Each redundant set of data may no longer agree with other sets of thesame data. When an RDBMS removes redundancy, inconsistency cannot occur.
• Data integrity: Data values stored in the database must satisfy certain types of consistencyconstraints. (We’ll discuss this benefit in more detail in the section “Understanding Data Integrity” later in this chapter.) 26 CHAPTER 3 n GETTING TO KNOW RELATIONAL DATABASES
• Data atomicity: In event of a failure, data is restored to the consistent state it existed in prior to the failure. For example, fund transfer activity must be atomic. (We cover the fund transfer activity and atomicity in more detail in Chapter 8.)
• Access anomalies: RDBMSs prevent more than one user from updating the same data simultaneously; such concurrent updates may result in inconsistent data.
• Data security: Not every user of the database system should be able to access all the data. Security refers to the protection of data against any unauthorized access.
• Transaction processing: A transaction is a sequence of database operations that represents a logical unit of work. In RDBMSs, a transaction either commits all the changes or rolls back all the actions performed until the point at which failure occurred.
• Recovery: Recovery features ensure that data is reorganized into a consistent state after a transaction fails.