Systems engineering is an interdisciplinary field of engineering that focuses on how to design and manage complex engineering systemsover their life cycles.
Software engineering is the study and an application of engineering to the design, development, and maintenance of software.
Software engineering is a part of System Design. In other words we can say that Software engineering is a subset of system engineering
both are clear from their names System Engineer in dealing with a whole system containing {Database Calculations processes and UI} But Software Engineer Deals with one part of the system