It sounds like you might have two tables with the same structure (same field names) but different values. In this case, we don't actually want to blend the data, because blending the data will match up rows from one table with the other table creating one really wide table. Instead we want one really long table.
Instead, extract one of the data sources and add the additional data from the second data source to the extract. The Product Help entry Adding Data to Extracts has detailed instructions for this method.
I hope this answers your question!