In modern applications, databases perform a very important function but the choice of a database system and additional libraries may affect the speed of the operations. The paper presents a time analysis concerning the performing of insert, update, delete and select operations on three database systems, MySQL 8.0, PostgreSQL 14.1 and Oracle 21c, cooperating with an application using Doctrine libraries. The obtained results showed differences between performing operations with and without object-relational mapping. In cooperation with the application, the operations were carried out the fastest using the PostgreSQL system. The Oracle system performed data selection faster without mapping on a large data set.