Madhavi Vaidya

A Relation in relational database is based on relational scheme, which consists of a number of attributes. A relational database is made up of a number of relations and relational database scheme.

RDBMS defines the integrity constraint for the purpose of holding ACID property. ACID property corresponds to A C I D, they are nothing but Atomicity, Consistency, Isolation, and Durability.

SQL or Structured English like Query Language (SeQUEL).

The process of requesting data from the database, and receiving the results back is known as a database query; hence the name, structured query language.

In SQL, they are nothing but the tables, which store the data defined in the database in a row and column format

Relational tables have six properties, which must be satisfied for any table to be classified as relational. These are as follows:
Entries of attributes are single valued: Entry in every row and column position in a table must be single valued. This means columns do not contain repeating groups.
Entries of attribute are of the same kind: Entries in a column must be of the same kind. A column which is supposed to store the salary of an employee, should not store commission.
No two rows are identical: Each row should be unique; this uniqueness is ensured by the values in a specific set of columns called the primary key.
The order of attributes is unimportant: There is no significance attached to the order in which columns are stored in the table. A user can retrieve columns in any order.
The order of rows is unimportant: There is no significance attached to the order in which rows are stored in the table. A user can retrieve the rows in any order.
Every column can be uniquely identified: Each column is identified by name, and not by its position and the order. A column name should not be repeated in the table.

The entity is a distinguished object.

A relation is a two-dimensional table with special properties.

A relational table consists of a set of named columns, and an arbitrary number of rows.

The relational model was defined in 1969 by scientist Edgar F. Codd. Relational model for managing databases, is a method that is used for managing data using a structure, where all data is represented in terms of tuples, finally grouped into relations.