Is it insecure to reveal a row's primary key to the user?

Why do many applications replace the primary key of a database with a seemingly random alternative id when revealing the record to the user?

My guess is that it prevents users from guessing other rows in 开发者_Python百科the table. If so, isn't that just false sense of security?

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I guess you are talking about surrogate keys here. One of the desired or supposed advantages of surrogate keys is that they aren't burdened by any external meaning or dependency on anything outside the database. So for example the surrogate key values can safely be reassigned or the key can be refactored or discarded without any consequences for users of the system.

Generally surrogate keys are kept hidden from users so that they don't acquire any such external dependencies. Being hidden from users was in fact part of the original definition of a surrogate key as proposed by E.F.Codd. If key values reside in the user's browser cache or favourites list then they aren't much use as "surrogates" any more. So that's one common reason why you will see one key used only inside the database and a different key for the same table made visible in the application.

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I think it may depend on the type of application you are working with. I work with Enterprise software that is only used by the company I work for and is not generally available to the outside world. In this case, it is often critical to let the user see the surrogate key for people-related records because the information in the person table has no uniqueness. There can be two John Smiths (we actually have over 1000 of them) who are genuinely different people. They may even have the same business address and be different people (Sons are often named for fathers and work in the same medical practice for instance). So they need to refer to the surrogate key on forms and in reporting to ensure they are using the record they thought they wanted. OItherwise if they wanted to research further details about the John Smith that they saw in a report, how would they look it up in the aaplication without having to go through all 1000 to find the right one? Creating a fake id as well as the real one would be time consuming (we import millions of records at a time) and for no real gain since the data would not be visible outside our comapny application.

For a web app that is open to the general public, I can see where you might not want to show this information.