How to list values once that reoccur
I have a data set I need to enter into a table. It is basically a city name with the corresponding postal codes. However, some cities have multiple postal codes.
For Example : Columbia - 29209, 29202, 29201
How can I include all the postal codes for each city, without listing the city multiple times. This would cause the pop up menu to have the city of Columbia on the list 3 times. I would like to only have it listed once.