SQL

 

A Database :

A database is a collection of data that is organized in a manner that facilitates ease of access, as well as efficient management and updating.

A database is mode up of tables that store relevant information.

For example, you would use a database, if you were to create a website like YouTube, which contains a lot of information like videos, usernames, password, comments.

Database Tables :

A table stores and displays data in a structured format consisting of  columns  and rows that are similar to those seen in Excel spreadsheets.

Databases often contain multiple tables, each designed for a specific purpose. For example, imagine creating a database table of names and telephone numbers.

First, we would set up coloumns with the titles FirstName, LastName and TelephoneNumber.

Each table include its own set of fields, based on the data it will store.

Primary Keys :

            A Primary key is a field in the table that uniquely identifies the table record.

The primary key's main features:

> It must contain a unique value for each row.

> It cannot contain NULL values.

For example, our table contains a record for each name in a phone book. The unique ID number would be a good choice for a primary key in the table, as there is always the chance for more than one person to have the same name.