What is SQL SQL Syntax

What is Rdbms

All modern database management systems like SQL, MS SQL Server, IBM DB2, Oracle, My-SQL and Microsoft Access are based on Rdbms.

Rdbms was developed by a jermen scientice mr. E.F codd at 1970 this model was developed on the basis of a mathematical concept called relational algebra.

E.F codd

Relations are classified into three types, they are;

  • 1:1
  • 1:M or M:1
  • M:M (many to many)

one-one Relationship

In this relationship one object have only one relation with another object.

one-one relationship

In above image one employee have only one emp_id. this is the example of 1:1 relationship

one-many or many-one Relationship

In this relationship one object have relation with many other object.

one-many relationship

In above image one faculty can teach many subjects. This is the example of 1:m relationship

many-many Relationship

In this relationship many object has the relationship with many other object.

many-many relationship

In above image one customer can purchase many items and one item can purchase by many customers, this is the example of m:m relationship

Properties of Rdbms

  • Data should be stored in the form of table.
  • A table can be defined as collection of rows and columns
  • The horizontal lines are known as row or tupples or record.
  • The vertical lines are known as column or field or attributes.
  • The intersection of row and column is known as cell.
  • A cell is a place where you can store your data.
  • The other name of table is called as entry or class or object.
rdbms properties

What is table

Rdbms are use table to store data, table are the collection of related data entries and row and column. Below is the simple example of table which store detail about employee.

101Amit Sukla29001
102Rahul jain43500
103Sultan Alam50000
104Gaurav rawat54000
105Hitesh Kumar43100

What is Field

Field is a smaller entity of the table which contains specific information about every record in the table. In the above example, the field in the Employee table consist of emp_id, name, salary.

What is row

Row is a part of table which is horizontally disply in table it is also called record. Row contains the specific information of each individual entry in the table. In below example row contain detail of Hitesh kumar records.

105Hitesh Kumar43100

What is column

A column is a vertical entity in the table which contains all information associated with a specific field in a table.

Amit Sukla
Rahul jain
Sultan Alam
Gaurav rawat
Hitesh Kumar

What is cell

A cell is a place where you can store your data.

What is SQL SQL Syntax


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