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Domain
Columns or Fields or Attributes 5000,100000
Primary
Key EMP_ID NAME POSTS Salary
E1 Rahul Clerk 30000
Rows E2 Kapil Manager 90000
Records Cardinality (No. of Rows) = 4
or Tuples E3 Manoj Clerk 90000
E4 Mukesh Peon 20000
Degree (No. of Columns) = 4 Data Value
Basic Terminologies of RDBMS
Some of the important terms of RDBMS are as follows:
• Entity: It is a real-world object about which information is to be stored in a database. For example, if we want to
store information about an entity Student in a school, then we need to have his admission number, roll number,
name, father’s name, date of birth, etc. These details associated with the entity are called attributes. Each entity
is a collection of these attributes associated with it. So, roll number, name, admission number, etc., are attributes
associated with the entity student. These attributes are represented in the form of columns.
• Tables: Tables are the basic structure of a database where data is stored. A table is a collection of logically related
records. It is organised as a set of columns and can have any number of rows. Each row represents a record, while
each column represents a field or attribute of that record.
• Data Values: Data values are the raw data represented in numeric, character or alphanumeric form.
• Fields/Columns: Fields or columns are the individual pieces of data stored within a table. Each field has a data type
associated with it, such as text, number, date, etc. A field is the smallest entity in the database. A collection of fields
makes a record, a collection of records makes a table, and a collection of tables make a database.
• Records/Rows: Records or rows are individual entries within a table. The data values for all the fields related to a
person or object is called a record. Each row represents a single instance of data, with each column containing a
specific attribute or value for that instance.
• Keys: A key is a field or combination of fields that uniquely identify a record (row) in a table. Keys are essential for data
integrity and for establishing relationships between tables in a relational database management system (RDBMS).
• Relationships: Relationships define how tables within a database are related to each other. Common types of
relationships include one-to-one, one-to-many, and many-to-many. These relationships are established using foreign
keys, which are fields in one table that reference the primary key of another table.
• Constraints: Constraints are rules that enforce data integrity within a database. They define the conditions that
must be met for data to be inserted, updated, or deleted in a table. Common types of constraints include primary
key constraints, foreign key constraints, unique constraints, and check constraints.
• Queries: Queries are commands or statements used to retrieve, manipulate, or analyse data within a database.
They allow users to perform tasks such as selecting specific records, calculating aggregate values, updating data,
and joining multiple tables together.
• Degree: This refers to the number of attributes or columns in a table. For example, if a table has five columns
(attributes), then the degree of the table is 5.
• Cardinality: This refers to the number of tuples or rows in a table. For example, if a table has 100 rows, then the
cardinality of the table is 100.
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