I want help with a database idea from any one.

I am trying to make a database which have one table of transactions in and one of transaction out, in which there will be transactions of more then one company (for eg.)

I need to figure out what should i do so that I can easily handle the records of the different companies, how should i maintain the records in it. is it even possible to handle more companies in one database ?

I will be searching like the remaining balances of the companies individually, and the transactions of the companies individually and by order too.

I am beginner.
Thanks if helped.