Relational databases have existed since the beginning of the seventies of the last century. In the meantime, applications that use data stored in databases, have changed. With the expansion of the Internet has increased the number of concurrent accesses to databases and the volume of data that need to be kept and be made available, it is highly increased. In the thesis we present a relational database, strengths and weaknesses. We will present the database NoSQL (Not Only SQL), which emerged as a response to the weaknesses of relational databases. We will show that NoSQL databases are not suitable for all modern Internet applications. One of them is an Internet application for the accounting program. To test the suitability of NoSQL databases for use within the accounting application, we will create a simple application that will use data from relational and NoSQL databases. We shall measure the speed of access to data with different queries.