topic Re: Add constraint comparing another field and NULL in ArcGIS Survey123 Questions

Add constraint comparing another field and NULL

DamianMilne — Wed, 15 May 2019 00:14:31 GMT

Hi, I have two integer fields, "FIELD A" and "FIELD B". I am trying to add a constraint on "Field A" that meets the following conditions:

If "Field B" IS NULL, "Field A" can be any value (including NULL)

If "Field B" IS NOT NULL, "Field A" must be greater than "Field B"

Can anyone assist with the syntax please?

Regards, Damian

Re: Add constraint comparing another field and NULL

DougBrowning — Wed, 15 May 2019 15:25:16 GMT

In 123 Null is empty string. So compare to '' or "".

Re: Add constraint comparing another field and NULL

JamesTedrick — Mon, 20 May 2019 22:31:59 GMT

Adding on to Doug's comment, use the function string-length(${q}) > 0 to test for null - all question types evaluate to a string length of 0 when null.

Re: Add constraint comparing another field and NULL

DamianMilne — Mon, 20 May 2019 23:40:07 GMT

Thank you gents, however the answer still alludes me. The closest I can come up with is the following:

if(string-length(${Field_B}) > 0,${Field_A} > ${Field_B},*** any number or NULL ***)

Any further assistance would be greatly appreciated.

Re: Add constraint comparing another field and NULL

DougBrowning — Tue, 21 May 2019 14:06:25 GMT

You just want it to eval to true so just give it a 1.

if(string-length(${Field_B}) > 0,${Field_A} > ${Field_B},1)

Re: Add constraint comparing another field and NULL

DamianMilne — Thu, 23 May 2019 05:37:53 GMT

Ahh, many thanks Doug.