I'm working on a validation rule for field service and I'm wondering if this is possible.

We have the Product Request parent object, and the Product Request Line Item child object. There is a field called "Part Number" on the PRLI - only one part number exists on a PRLI, so a new PRLI needs to be created for each part number. Due to interface concerns, we want to prevent a PR from being saved if there are more than one PRLI with the same value in the Part Number field (because the tech should be adjusting the quantity on the PRLI, not creating multiple PRLIs for the same part number). Is it possible to write a validation rule on the parent object that checks a field on the child for duplicates?

1 Answer 1


No, it is not possible for a validation rule to check child records.

Duplicate Rules is a feature worth looking into. If that's not an option, then I think you'd need a trigger to accomplish this.

  • Thank you - would it be possible for a validation rule at the child level to check the field value against other child records? for example, a rule on the PRLI that checks the part number field on existing PRLIs for the same product request and verifies against that?
    – Sarah
    Jul 20, 2022 at 14:35
  • 1
    Duplicate Rules function similarly to validation rules in that they prevent save when certain conditions are met. And no, a VR on PRLI won't work either. Jul 20, 2022 at 14:47

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