Provided is a system and method for combining feature sets of data via single vertical union operation. In one example, the method may include receiving a plurality of tables corresponding to a plurality of features observed from a dataset for use in machine learning, identifying columns of features within the plurality of tables which are to be combined, concatenating the identified columns of the features based on a union operation which sequentially appends the identified columns to each other, and storing the concatenated columns of the features as a combined dataset.