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Location

IP: 209.85.175.132

continent: NA, country: United States (USA), city: Mountain View

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Basic information

website build using CSS

code weight: 93.47 KB

text per all code ratio: 20 %

title: Mirko Marović - in English

description:

keywords:

encoding: UTF-8

language: en

Website code analysis

one word phrases repeated minimum three times

two word phrases repeated minimum three times

three word phrases repeated minimum three times

B tags

Obviously if a key changes very often, or will be used as a FK for many other tables, there can be performance or concurrency implications to making it the primary key .  In this case, you do want toconsider a surrogate, and use it if appropriate. The problem in Galenika was not that a key was changed very often. It was enough that its structure changed once and for all products. I don't know in how many tables that code was foreign key, however the main problem, and huge one itself, was that it was foreign key in sales transactions table. So, my recommendation is not to consider a surrogate, but to use a surrogate and not even think about "natural" key. Even if you don't have "FK for many other tables

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Which side is right?  Neither.  Both natural and surrogate keys have their own place, and a developer who doesn’t use both as the situation demands is shortchanging both himself and his applications.

The value of a surrogate must never be exposed to the outside world.   Users should never be allowed to see the key, under any conditions.   Display the value of a surrogate key on a report, allow it to be viewed on a form or even used as a search term – these are all forbidden.   Once you expose a surrogate key, it immediately begins acquiring business meaning. 

Note: if your data already contains meaningful product codes or other keys such as those described above, then they are simply natural keys and the above caveat doesn’t apply.     It’s a smart key only when the value is constructed by the developer.

Immutability is certainly a desirable feature for a key, but it’s by no means a requirement.   Using this as an excuse is the trademark of a lazy developer.  Data changes.   If the key changes, update it.  If it’s being used as a foreign key in another table – update that table too.  Cascading updates exist for a reason, after all.

Obviously if a key changes very often, or will be used as a FK for many other tables, there can be performance or concurrency implications to making it the primary key .  In this case, you do want toconsider a surrogate, and use it if appropriate. 

consider a surrogate,

FK for many other tables

Replacing a wide key with a narrower value means smaller indexes, and more values retrieved from every index page read.  This does boost performance.  However,  you’ll usually retain the index on the natural key (to enforce uniqueness if nothing else) and that means another index to maintain.  If your table is very narrow, the additional column for the surrogate can noticeably impact performance and storage requirements.

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