Primary Field Allowing Non-Unique Entries

[lmm7186]

Hello, I'm working on a new database and one of my tables includes various types of barcoding equipment.  Each record should have its own unique Serial Number, so I made Serial Number my Primary Field for that table.  I thought that, by default, the Primary Field always required unique values but I've just tried entering a duplicate S/N and it allowed the entry.

How can I make sure my Primary Field doesn't allow for the same value to be entered more than once?

[Alexey_Gusev]

It is recommended but not required. Airtable has no special built-in check constraint, but you can create automation for that. To perform 'soft-tracking', you can change summary type to 'Unique'. If the number of unique value less than number of records, then you have duplicates.