Database-wide unique-yet-simple identifiers in SQL Server

Question

First, I\'m aware of this question, and the suggestion (using GUID) doesn\'t apply in my situation.

I want simple UIDs so that my users can easily communicate this i

Answer 1

I use a high/low algorithm for this. I can't find a description for this online though. Must blog about it.

In my database, I have an ID table with an counter field. This is the high part. In my application, I have a counter that goes from 0 to 99. This is the low part. The generated key is 100 * high + low.

To get a key, I do the following

initially high = -1
initially low = 0

method GetNewKey()
begin
  if high = -1 then
    high = GetNewHighFromDatabase

  newkey = 100 * high + low.
  Inc low
  If low = 100 then
    low = 0
    high = -1

  return newKey
end

The real code is more complicated with locks etc but that is the general gist.

There are a number of ways of getting the high value from the database including auto inc keys, generators etc. The best way depends on the db you are using.

This algorithm gives simple keys while avoiding most the db hit of looking up a new key every time. In testing, I found it had similar performance to guids and vastly better performance than retrieving an auto inc key every time.