Locating Data and Special Numbers
SQL implementations come with proprietary features to help locate data in physical storage. Some of these features are taken from the hardware and some are independent of it. Sequential numbers, random numbers, and mathematical series with special properties are the most popular.
SQL is supposed to use keys. Keys are a logical concept that is divorced completely from physical storage. Unfortunately, bad SQL programmers will use proprietary features to get the hardware to generate exposed physical locators. These numbers represent an event or location in the hardware and have nothing whatsoever to do with the logical model.
Do not confuse exposed physical locators with surrogate ...