This question already has an answer here:

I want to label a layer with 2 columns/attributes. It´s not a problem in Mapinfo, but can it be done in QGIS as well?

merged by underdark Jun 5 '15 at 13:24

This question was merged with Concatenating fields in field calculator of QGIS? because it is an exact duplicate of that question.

Browse other questions tagged or ask your own question.