At first before going into sql concepts,

think about data.

What might be the data means?

Everyone tells about - data, data, data ….

it's simple, any information that we need to store known to be data.

example: A businessman named Ram, had a small store where let it be 10 customers will shop each day, so Ram want to know what all things does his customers buying every time. So that he can get that products more into his store get many more customers. In this situation if Ram had a Excel in his laptop, as daily he had approx 10 customers so he himself can enter the items in the excel sheet. Here whatever he enters into the excel sheet known as data in technical terms.

Do we really want data?

One thing we need to notice that,

When it comes to any company or any businesses, end of the day it's all about money.

In olden days there used to be papers to write and store them for any reference in further.

But later, computers invented and then every small and large business shifted to it.

To store their accounts and documents (everything like employee name, salaries, contact details etc)

By storing the data like that from years, it was huge data in every business/ company.

So then prediction has started, it is to predict how the upcoming years sales might be in company!/business.

Even if there is any company in losses, by help of previous years data, there is a high chance to get of the loss.

How is it possible?

for every company there will be set customers who purchase their product that's how it works.

And any of time from the establishment of that company, It might came across huge success and sometimes loss as well.