RDBMS terminologies

RDBMSDatabaseMySQL

RDMS Terminologies include Database, Table, Columns, etc. Let us see them one by one −

Database

Database is a collection of tables like <Student>, <Professors>, etc.

Table

A table is a collection of rows and columns , for example,

StudentId
StudentName
StudentRank
052
Tom
1
035
David
2
077
John
3

Column

Column is in a table −

Row

Row is also called a tuple in RDBMS. 

A relation in a database has rows and columns.

Primary Key

Every table has one Primary key and cannot have null values.

For example, ProjectID is a primary key in Project Table, since it uniquely identifies the project:

ProjectID

ProjectName

P01
Cluster Grouping System
P02
Hospital Management System

Foreign Key

If you want to link two tables, use Foreign Key.

For example, Employee table has DEPT_ID that is a foreign key, which is linked to Department table.

The Department table has primary key DEPT_ID.

Super Key

Super Key is an attribute (or a set of attributes) that uniquely identify a tuple i.e. an entity in entity set. It is a superset of Candidate Key, since Candidate Keys are selected from super key.

Composite Key

A primary key having two or more attributes is called composite key. It is a combination of two or more columns.

raja
Published on 04-Jul-2018 13:45:15
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