For some reason I lost my previous question here but I proceeded a little bit after upgrading to the newer version of QGIS.
My problem was combining spreadsheet .csv data to the .shp map layer, where the joining and target field were building values and it only recognized the first feature and missed all the other features coming from the same building. I managed to do a join with join attributes by field value (one-to-many) and the joined table now includes all the features.
Now I'm trying to join this new joined table to building point data map layer .shp, but it does the same thing again leaving the duplicate values out (building value). How can I add this joined table with all the features in it to the point data map layer .shp? Should I use different join values? I can only join the spreadsheet and building data with a certain building value.