Removing columns

In the first example, let's delete some values from our administrative boundaries layer. If we inspect its attribute table, we can see some unnecessary columns. In my table, ID_0 and CCN_1 have constant values, which have absolutely no meaning to me. The CCA_1 and NL_NAME_1 columns are filled with null values, while VARNAME_1 is scarcely filled, therefore, I cannot use them. Let's pick every unnecessary column and remember their names. In the attribute table's toolbar, we can see some tools related to data management. We can add and remove columns; however, those options are disabled. We can enable them by starting an edit session by clicking on the first, Toggle editing mode button. With the editing options enabled, we can proceed by activating the Delete field tool, selecting the columns we would like to remove, and approving the operation with the OK button:

When the operation stops, we can see our unnecessary columns removed. If we save our edits, QGIS overwrites our layer and they are gone for good. Of course, we can change our mind or realize we accidentally removed some important data. In this case, we can restore the original conditions by not saving our edits.