Warehouse of Information
- The database management systems are warehouses of information, where large amount of data can be stored. The common examples in commercial applications are inventory data, personnel data, etc. It often happens that a common man uses a database management system, without even realizing, that it is being used. The best examples for the same, would be the address book of a cell phone, digital diaries, etc. Both these equipment store data in their internal database.
- The unique data field in a table is assigned a primary key. The primary key helps in the identification of data. It also checks for duplicates within the same table, thereby reducing data redundancy. There are tables, which have a secondary key in addition to the primary key. The secondary key is also called 'foreign key'. The secondary key refers to the primary key of another table, thus establishing a relationship between the two tables.
- The data is stored in the form of tables. The tables consist of rows and columns. The primary and secondary key help to eliminate data redundancy, enabling systematic storage of data.
Changes to Schema
- The table schema can be changed and it is not platform dependent. Therefore, the tables in the system can be edited to add new columns and rows without hampering the applications, that depend on that particular database.
No Language Dependence
- The database management systems are not language dependent. Therefore, they can be used with various languages and on various platforms.
- The data in two or more tables can be integrated into a single table. This enables to reduce the size of the database and helps in easy retrieval of data.
Multiple Simultaneous Usage
- The database can be used simultaneously by a number of users. Various users can retrieve the same data simultaneously. The data in the database can also be modified, based on the privileges assigned to users.
- Data is the most important asset. Therefore, there is a need for data security. Database management systems help to keep the data secured.
- Different privileges can be given to different users. For example, some users can edit the database, but are not allowed to delete the contents of the database.
Abstract View of Data and Easy Retrieval
- DBMS enables easy and convenient retrieval of data. A database user can view only the abstract form of data; the complexities of the internal structure of the database are hidden from him. The data fetched is in user-friendly format.
- Data consistency ensures a consistent view of data to every user. It includes the accuracy, validity and integrity of related data. The data in the database must satisfy certain consistency constraints, for example, the age of a candidate appearing for an exam should be of number datatype and in the range of 20-25. When the database is updated, these constraints are checked by the database systems.
The commonly used database management system is called relational database management system (RDBMS). The most important advantage of database management systems is the systematic storage of data, by maintaining the relationship between the data members. The data is stored as tuples in a RDBMS.
The advent of object-oriented programming gave rise to the concept of object oriented database management systems. These systems combine properties like inheritance, encapsulation, polymorphism, abstraction with atomicity, consistency, isolation and durability, also called ACID properties of DBMS.
Database management systems have brought about systematization in data storage, along with data security.