I will be making a large accounting software using PHP. So I am wandering which database to use?

Shubroto;

I am a huge NoSQL (MongoDB) fan and would certainly encourage you to go through the new Mongo Basics course. There are other NoSQL options available as well, but I will concentrate on MongoDB here.

With that being said, applications like double entry accounting systems are not MongoDB's strong suit. Why not? Three main reasons that I can think of.

1. While most real world data is not tabular, accounting system data is. Thus it is a great use case for a relational database.
2. Accounting systems have complex multi-row transaction operations. MongoDB's support for transactions is limited in order to provide better horizontal scaling. Thus not being an ideal fit.
3. Your database will likely not be huge and, therefore, not require MongoDB's sharding capabilities.

For the accounting system then I would steer you towards a relational database and MySQL would be well suited for that. There is SQL Basics course on Treehouse that is a great starter for relational databases. Depending on your use case for the application a combination of a NoSQL and SQL databases is often used, with SQL handling transactions (accounting) and NoSQL (MongoDB) handling other information.

In terms of power, ease of use, and security, I think they are likely equivalent given a similar knowledge base on each system. It is more of a matter, in my opinion, of choosing the correct tool for the job.

Hope that helps and post back if you have further questions.

Happy coding,
Ken