In most cases, you shouldn't need to change the primary field in your table. However, if you need to do so, such as after importing a CSV, we recommend that you first create a new, empty column. Then, click the primary field header cell to select all cells in the column, then use Ctrlx (x on Mac) to cut those cell values. Next, you'll paste those values (Ctrlv/v) into the empty column. Finally, you can copy and paste cell values from another field into the primary field.