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The Question
How can I create a Calculated column with a formula that works the same way as an Excel MAX formula?

Why
I have a need to create unique ID's for process documents, but can't rely on the inbuilt ID field becuase if you delete a record SharePoint still reserves the ID for it. So there are no gaps in the set of Process Numbers I need to manually create this number.

Obviously I can do this by restricting entry of the number field to unique numbers but this wouldn't stop someone from entering 50 when there are only 30 records.

So ideally I was hoping to set the ProcessNumber field's default value as the result of =MAX(ProcessNumber)+1, but I have no idea how to.

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Calculated columns don't work "vertically" in the library, only "horizontally" that is they cannot be used to determine something about any other items, only the current item. You could set a process number via workflow, event receiver, or possibly use the document id feature which gives each document a unique id apart from the list item id.

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  • Thanks @PirateEric, just figured that out muself too, should have know that :( I think the Document ID would have same issue as the list ID. How would you recommend doing it by workflow? (I only have Designer)
    – CLockeWork
    Aug 6 '13 at 15:35
  • You have to store the current max in a list, then on item creation, you have to look that up, add 1 to it, update the current item with that then update the list as well. You also have to introduce a "soft delete" option so users can flag the item for deletion, the lookup your current max, subtract 1 and update that value.
    – Eric Alexander
    Aug 6 '13 at 16:09
  • Thanks @PirateEric, and sorry to keep asking questions, but how would I get the current max into another list if I can't get the max in general?
    – CLockeWork
    Aug 7 '13 at 13:49
  • You have to seed the list with a value, so if its a fresh library, you set the list value to zero, then start calculating off it.
    – Eric Alexander
    Aug 7 '13 at 15:43

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