Over the years, there has been a slow but increasing focus on the column-oriented database management systems (DBMSs). Column-oriented DBMSs are different from the traditional ones in the way data is stored and accessed. Traditional ones store data row-wise while the column-oriented ones store the data column-wise. This allows column-oriented DBMSs to have extensive usage in various data warehouse applications because of their better performance in terms of read I/O in comparison to the conventional DBMSs. This is primarily due to the fact that column-oriented DBMSs only retrieve the columns defined in the query rather than the entire row in case of traditional DBMSs. In this paper, we study some of the existing and latest open-source column-oriented database management systems. Our approach is to highlight the salient features unique to the system. We also compare the DBMSs on the basis of some integral database features such as indexing, compression, transaction handling, etc. In addition, we give a concise but comprehensive summary of the commerical DBMSs using column-oriented architecture.