How do I "validate" a column/field only if it's not blank

Question

I currently have a column called "MAC Address" - it is not a required field as some pieces of gear do not have an address, but unique values are enforced. If a user puts in an address I want to (at minimum) verify that the format is correct. I currently have the following in the "Column Validation".

=(LEN([MAC Address])=17) +(MID([MAC Address],3,1)=":") +(MID([MAC Address],6,1)=":") +(MID([MAC Address],9,1)=":") +(MID([MAC Address],12,1)=":") +(MID([MAC Address],15,1)=":")=6

However, with every new entry, it flags it as an error because an empty field does not solve this formula. From the pieces I have read online it might be solved with an "OR" or "ISBLANK", but I can't get the right syntax.

Can someone please tell me how to add the additional coding to make this only trigger if the field is NOT blank. Thanks so much!

Answer 1

Just add ISBLANK to your formula like this:

=IF(ISBLANK([MAC Address]),6,(LEN([MAC Address])=17) +(MID([MAC Address],3,1)=":") +(MID([MAC Address],6,1)=":") +(MID([MAC Address],9,1)=":") +(MID([MAC Address],12,1)=":") +(MID([MAC Address],15,1)=":"))=6

UPD: or

=OR(ISBLANK([MAC Address]),AND(LEN([MAC Address])=17,MID([MAC Address],3,1)=":",MID([MAC Address],6,1)=":",MID([MAC Address],9,1)=":",MID([MAC Address],12,1)=":",MID([MAC Address],15,1)=":"))