RDBMS stands for Relational Database Management System.
It is a program used to maintain a relational database.
RDBMS forms the foundation for all modern database systems, including MySQL, Microsoft SQL Server, Oracle, and Microsoft Access.
RDBMS utilizes SQL queries to access data within the database.
A table is a collection of related data entries organized into columns and rows.
A column contains specific information about every record in the table.
A record (or row) represents each individual entry in the table.
Consider a selection from the Northwind “Customers” table:
|
CustomerID |
CustomerName |
ContactName |
Address |
City |
PostalCode |
Country |
|
1 |
Alfreds FutterKiste |
Maria Anders |
Obere Str. 57 |
Berlin |
12209 |
Germany |
|
2 |
Ana Trujillo Emparedados y helados |
Ana Trujillo |
Avda. de la Constitución 2222 |
México D.F. |
05021 |
Mexico |
|
3 |
Antonio Moreno Taquería |
Antonio Moreno |
Mataderos 2312 |
México D.F. |
05023 |
Mexico |
|
4 |
Around the Horn |
Thomas Hardy |
120 Hanover Sq. |
London |
WA1 1DP |
UK |
|
5 |
Berglunds snabbköp |
Christina Berglund |
Berguvsvägen 8 |
London |
S-958 22 |
Sweden |
The columns in the “Customers” table are: CustomerID, CustomerName, ContactName, Address, City, PostalCode, and Country. The table contains 5 records (rows).
A relational database organizes data into tables, where tables are interconnected based on shared data.
Consider the following three tables: “Customers,” “Orders,” and “Shippers” from the Northwind database:
|
CustomerID |
CustomerName |
ContactName |
Address |
City |
PostalCode |
Country |
|
1 |
Alfreds FutterKiste |
Maria Anders |
Obere Str. 57 |
Berlin |
12209 |
Germany |
|
2 |
Ana Trujillo Emparedados y helados |
Ana Trujillo |
Avda. de la Constitución 2222 |
México D.F. |
05021 |
Mexico |
|
3 |
Antonio Moreno Taquería |
Antonio Moreno |
Mataderos 2312 |
México D.F. |
05023 |
Mexico |
|
4 |
Around the Horn |
Thomas Hardy |
120 Hanover Sq. |
London |
WA1 1DP |
UK |
|
5 |
Berglunds snabbköp |
Christina Berglund |
Berguvsvägen 8 |
London |
S-958 22 |
Sweden |
The relationship between the “Customers” table and the “Orders” table is established through the CustomerID column.
|
OrderID |
CustomerID |
EmployeeID |
OrderDate |
ShipperID |
|
10278 |
5 |
8 |
1996-08-12 |
2 |
|
10280 |
5 |
2 |
1996-08-14 |
1 |
|
10308 |
2 |
7 |
1996-09-18 |
3 |
|
10355 |
4 |
6 |
1996-11-15 |
1 |
|
10365 |
3 |
3 |
1996-11-27 |
2 |
|
10383 |
4 |
8 |
1996-12-16 |
3 |
|
10384 |
5 |
3 |
1996-12-16 |
3 |
The relationship between the “Orders” table and the “Shippers” table is defined by the ShipperID column.
|
ShipperID |
ShipperName |
phone |
|
1 |
Speedy Express |
(503) 555-9831 |
|
2 |
United Package |
(503) 555-3199 |
|
3 |
Federal Shipping |
(503) 555-9931 |