Database Management System ( Dbms )

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2. What is a DBMS? Briefly describe the components of a DBMS.
Database Management System(DBMS) is a collection of interrelated data (database) and set of programs to access and modify those data.
DBMS has several components. Each component has some specific task to perform. The Major components DBMS are as follows,
Hardware
Without hardware it is not possible to implement DBMS. The main hardware is the computer used for storing and accessing the data in database. Other hardware components used in DBMS are Storage devices, I/O devices, and electromechanical devices which makes interface between user and the database.
Software
This is main component of the DBMS. Software is the set of programs to access and control the data in the
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Granting of authorization for data access iv. Routine maintenance

End Users
The real users who the application programs to interact with the database to perform different operations stored in the database. Some of the operations are insertion, deletion, updating data in the database, etc.
Query processor
It converts the user queries into series of low level instructions. The query processor has the following components,
i. DDL interpreter:
It interprets DDL statements and records definitions in the data dictionary. ii. DML compiler:
It translates DML statements in the query language into an evaluation plan consisting of low level instructions. iii. Query evaluation engine:
It executes low level instructions (query evaluation plan).
Data
Data is the most important component of the DBMS. The main purpose of DBMS is to process the data in efficient and convenient way for the users. In DBMS, databases are defined, constructed, modified , inserted and accessed from the database. There are two types of data in the DBMS. They are
i. Meta data:
It is the data about data or description about data stored in the database. Data definition language(DDL) is used to manipulate this type of data. ii. Actual data:
This is data actually stored in the database by the users. Data manipulation language(DML) is used to manipulate this type of data.

3. Describe a primary key, candidate key, secondary key, foreign key, and a combination
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