I have a .shp file of a country in which I have NAME_1 as state/province name. NAME_2 as district name and NAME_3 as towns of the district. I want to merge the polygons based on NAME_2 for the whole country except 30 entries out of them. I tried dissolve tool of QGIS but it didn't helped. There is one more problem here is that NAME_2 can be repeated for more than one NAME_1. So I have to take care of this also. I am doing it manually one by one using merge selected features in QGIS. Could somebody show me a way for doing this as fast as possible.
1) Create a new field called Name_12 which would be a concat("NAME_1",',',"NAME_2") in order to solve the problem of the same district name for different states and use this as the dissolving field.
2) Select the 30 polygons that i don't want to dissolve and then do a reverse selection to select the rest and run the dissolve.