What important information is stored on databases and why?

Database contains relevant and important information that is often needed for a certain program or application such as console application or a website.

The following example will show a situation with a use of a database:

An owner of a website has a large amount of customers.

He wants his website to display a suitable text for a suitable customer. for that he needs to make the website to identify which customer has entered the website.

Now, he could make a login form, but the login script needs to check the username and the passWord from some sort of an information tank.

SQL is the language that "speaks" to the database.

There are four main actions in SQL:

* Select - used to pick up information

* Insert - used to add a new row to the database's table

* Update - used to edit column(s)

* Delete - used to delete row(s)