Adding Null value symbology?

Question

Hi, I have a symbology which is set through two attributes using unique values. For example the values would be 800,100 801,100 in my database there is a combination of this two fields with a value For example: 800; and this is picked up in the symbology when I do, add all values Now I also want to add 801; to this symbology posibilities, now this combination is not present yet in the attribute table but could be in the future. Yet when I try to do this via the "add values" option in the symbology pane I always get an error: I tried several different options of null, " ", , Null, but nothing works The field from the is a numeric long integer field. How can I add this to the list??

AndreasB · Answer

Nothing didn't work unfortunatly.

I'm currently working with map services that are read only so I can't temper with the data.

I mainly to know why it does get taken into account when it's in the attribute table but when the combination is not and you want to add it you get a warning that this value is not allowed.

clt_cabq · Answer

Does using the term Nothing instead of Null work? In calculations where you want to make a field's value  null you use an expression like  'FieldName = Nothing' so this makes me wonder if that will work here.

DavidSolari · Answer

Make a copy of the feature class, ensure it has the same symbology as the source layer, add records which contain the values you want to symbolize, add those options to the unique values, configure the symbols, save this to a layer file, apply this layer file to the source layer, delete the copy. Boom, you're ready for future data without tampering with the production features!