Database Management System (DBMS)
Database Management System (DBMS)
In this tutorial you will learn about Database Management System (DBMS), advantage and disadvantage of Database management system, Architecture,
Key in Database Management System etc. about (DBMS).
What is Database Management System?
A Database Management System (DBMS) is a computer program designed for creating and managing the database. It provides a systematic way to run operations like creating, retrieving, storing data, deleting data from the database. It serves as an interface between the database and end users. It also provides protection and security to the databases.
Example; MySQL, SQL, SQL Server, IBM DB2, PostgreSQL, Amazon Simple DB, (Cloud based) are some popularly used DBMS.
Advantage of DBMS –
- Data security and consistency
- Reduced Data redundancy
- Easily accessible
- Better data transferring
- Integrity Constraints
Disadvantage of DBMS –
- Frequency Upgrade or Replace Cycle
- Large in size
- Difficult Backup and Recovery
- Licensed DBMS are costly
Architecture (Level of Data Abstraction in DBMS)
Database system consist of complex data structure. The process of masking irrelevant information from users is known as Data Abstraction. Data abstraction reduced the complexity of users with the database. Three levels of data abstraction are Physical Level, Logical Level and View Level.
The Architecture of commercial DBMS is based on ANSI-SPARC database architecture.
View Level/Internal Level –
It is the highest level of abstraction and is viewed by the user in terms of tables and relations. It describes only a part of the entire database and hides the details of the logical level.
Physical Level/Internal Level –
It is the lowest level of abstraction. It describes how the data is physically stored in detail. B+ tree, Hash file organization methods are used in this level.
Logical Level/Conceptual Level –
It is the next level of abstraction and describes what data is stored and what is the relationship among that data. At the logical level, each record is described by a type and the interrelationship of these record types. Database administrators work at this level of abstraction. The changes which are done at this level will not affected the external or physical levels of data.
Keys in Database Management System
A key is a field in the database which is used to retrieve and sort rows in the table. Keys are used to speeding up the data accessing and creating links between different tables.
Types of Keys in DBSM –
Super Key – It is a set of one or more attributes whose values uniquely determine each entity in the database table. It is a subset of a candidate key.
Candidate Key – It is a set of columns in the table form which primary key can be selected to identify each record. Every database table may have one or more candidate keys.
Primary Key – It is a special key that uniquely identifies each record in the table. It has unique value for each row of data and it cannot contain null values.
Alternate Key – All keys except primary key are known as Alternate. Alternate keys are also called Secondary Keys.
Foreign Key – Foreign key points to the primary key of another table. It acts as a reference between tables. It can accept the null and duplicate value.
Composite Key – It is a combination of more than one column in the table that can be used to uniquely identify each record. It is also known as a Composed Key.
So, in this tutorial you learned Database Management System (DBMS), with advantage and disadvantage of DBMS, Keys in Database Management System etc. I hope you read this tutorial well and learn something new.
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