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Asked: 2026-05-28T05:08:00+00:00

I have two columns in a table that will always be unique, vendor_identifier and

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I have two columns in a table that will always be unique, vendor_identifier and product_identifier. Both of them are about equal length. Should I add both of them as primary keys, or only one, or some variant of that? Is there any difference between adding one or two here?

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  1. Editorial Team

    You can only have one be the primary key. You can have the other be a UNIQUE key.

    Whichever you prefer to be the default PRIMARY KEY is your choice.

    There is something you need to ask yourself:

    • Will a table that has both columns allow multiple products?
    • Will a table that has both columns allow multiple vendor?
    • Will a table that has both columns allow the tuple (vendor,product) one or more times?

    Answering these rhetorial questions will help you decide whether a table has one of the following as the PRIMARY KEY

    • vendor_identifier
    • product_identifier
    • vendor_identifier,product_identifier
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