2016
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Advantages of DBMS Programming Assignment Help
Programming Assignment Help
Augustine Barlow
The DBMS has lots of advantages over traditional computer file processing. The main features of DBMS are as given below: Data Redundancy Control: In traditional file processing system, each application program has its own files, which results in duplicate copies of same data at different locations. In DBMS, all the data is integrated into a single database and recorded at only one place in the database. Hence it avoids duplication of data. In DBMS, the data redundancy can be reduced but can not be removed completely. In few cases, it becomes necessary to have duplicate copies of the same data so that we can create relations between tables. This feature of DBMS helps us in saving storage space. Also it is useful to retrieve data from database using queries. Data Consistency: Data consistency is achieved with the help of data redundancy control. Because there is only one set of data is the part of database, hence any update on this data will be performed only once and new updated value will be available to all users. In case minimal/required redundancy exists in DBMS, then each value corresponding to that data item will be updated automatically by DBMS. Data Sharing: In Database Management System, data can be shared with the authorized users only. Database administrator manages the data and provides access of the data to users based on roles and responsibilities. Multiple users can access same set of data simultaneously. The same data can be used by different application programs. Integrity Constraints: Integrity constraints are applied to database so that only correct data can be inserted into database. The constraints may be applied to data item in a single record or it may be applied to relationships between different records of different tables. Some of the major constraints used by DBMS are as given below: Constraint Name Primary Key Foreign Key Unique Not Null
Description Columns designated as Primary Key can not have duplicate values and can not have null values This constraint is used to establish relationship between tables Columns having this constraint can not have duplicate values Columns having this constrain can not be left blank
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These integrity constraints applied during the design phase of database. DBMS applies these integrity constraints when data is being inserted into the database or existing records gets updated. E.g. Salary paid to the employees at the month end is being calculated based on the number of days, employee was present in the office. Hence Payroll and Attendance modules are having inter-related tables and data from Employee master is referred during such processes. Data Security: Data security is something which protects data from unauthorized users. Only authorized users can access the data and database. Access is provided based on user’s roles and responsibilities in the organization i.e. one set of data can be accessed by one group of users and it is not accessible to another group of users. Usually administrators or top management is having full access of data. DBMS allows read/write operations on dataset to one set of users while other group of users is having only read access. DBMS also permits to have data access within defined time frame only and post that data is not accessible to the users. Only administrators can access the data and database. Backup and recovery: In file based transaction processing system, user has to create data backup manually to protect the important data from damaging in case computer system or application gets failed. It was a time consuming process for large volume of data. Most of the DBMS provide the 'backup and recovery' option (sub-program) that automatically creates the backup of data at defined intervals and restores the data whenever it is required. E.g. if a system/application stops working in between of a transaction, the DBMS will restore the database to its previous state. Another example may be to take backup of old data which is not being used currently and restore it from tape drives/external drives when it is required. Entity: An entity is an object for which data must be captured. All things are not entities but the only things for which information is being captured, termed as Entity. Information about entity is captured in the form of attributes/relationships. If there are no attributes or relationship exists, then it cannot be termed as an Entity. Attributes: An attribute defines information about an entity that must be captured. Each entity has one or more attributes. Each entity instance has one value for each of its attributes. Value of an attribute can be numeric or character or spring or any other data value.
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