Understand databases and data management systems Key issues and application of databases within organization Database system or database is a collection of interrelated data with a set of programs to access that data. The main purpose of such a system is to provide an environment that can be used efficiently, easily and in convenient manner to retrieve and store information
5/3/2016
Database system or database is a collection of interrelated data with a set of programs to access that data. The main purpose of such a system is to provide an environment that can be used efficiently, easily and in convenient manner to retrieve and store information. A database management system (DBMS) is designed to manage a large information. Data management involves defining data structures for storing information/data and providing a mechanisms to manipaulate data/information. Apart from this, the database system must provide safety of the stored data/information even system crashes or attempts are being made to unauthorized access. If stored data is being accessed by multiple users concurrently, then DBMS shall maintain data integrity. Examples of the use of database systems are airline reservation systems, banking, payroll processing, employee information systems, credit card processing systems, sales and order tracking systems etc. Below are the key issues which were addressed post introduction of database management system (DBMS). Key issues addressed by DBMS: •
Reduced application development time: DBMS helped a lot in reducing the application development time as DBMS stores data in structured manner and based on that data, application development is much easier as compared to old methods of data store where data is stored in files and applications are being developed on that. Whenever there is a change in underlying data, everything needs to be changed i.e. files where data is stored, applications developed on top of that etc.
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Redundancy: DBMS helped in removing redundancy of data with the help of reference to the data that is stored once. We can use reference to the data wherever it is required and avoid storing duplicate data.
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Integrity: Data integrity puts a validations on the data which needs to be stored in database. This is achieved by integrity constraints or triggers which prevents insertion of invalid data to the database.
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Consistency: Consistency ensures that only valid data is written to the database. If, for any reason, a transaction is executed that violates the database’s consistency rules, the
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complete transaction will be rolled back and the database will be restored to the previous consistent state. In case transaction gets successfully executed, the database will move from one state that is consistent with the rules to another state that is also consistent with the rules. •
Data security: Data security is achieved by DBMS in such manner that only authorized users can access the data. We can restrict the data access based on roles and responsibilities.
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Data access control: Data access control is something that defines which data should be accessed by whom. Before DBMS, it was not possible to put control on data access and all data was accessible to all the users ir-respective of roles and responsibilities.
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Data backup and recovery: Older data can be archived and moved to external storage such as tape drives based on purging/archival policies of organization. This data can be restored as and when it is required. Earlier it was also a challenge to backup the old data and then restore it in case it is required.
Database Keys: Primary Key: Primary key is one of constraint imposed on database tables to keep unique data in tables. Columns marked as primary key will hold only non-duplicate values and will not accept empty values. Foreign Key: A primary key of one table that appears as an attribute in another table (foreign key) and acts to provide a logical relationship among the two tables. Super Key: Super key is set of attributes within a table that uniquely identifies each record within a table. Super key is the subset of Candidate key. Candidate Key: Candidate key are the columns/attributes from which we can select Primary Key. It is an attribute or set of attributes that can act as primary key for a table. Composite Key: Combination of two or more attributes to uniquely identify an entity is known as composite key. Example: A student can only be in one place at a time. Student Date Period Present J. Smith 01/07/14 1 Y Rogers 02/07/14 2 N Programming Assignment Help
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H. Rose
01/07/14
1
Y
In above example, combining the student name, date and period gives a unique value for each record.
Above are common features supported by any Database management system. Since DBMS is used mainly for business applications, major benefits of having a DBMS are as below: 1. Data Availability 2. Reduced redundancy 3. Data accuracy and consistency 4. Improved data security 5. Easiness in data management 6. Structured organization of data 7. Easy retrieval of data 8. Concurrent access of data to users Below diagram illustrates the example of DBMS in banking where customer data is stored in database and is accessed across multiple departments:
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