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copied!<p>You could leverage SQL Server's <a href="http://technet.microsoft.com/en-us/library/ms186775.aspx" rel="nofollow">IDENTITY</a> mechanism for this, because it's easy to use and handles concurrency well.</p> <p>More specifically, you could create three tables that contain only an identity (auto-incremented) <code>Id</code> column, using this script:</p> <pre><code>create table RedCardIds(Id int identity(1, 1) primary key) create table BlueCardIds(Id int identity(50001, 1) primary key) create table GreenCardIds(Id int identity(100001, 1) primary key) GO </code></pre> <p>The three tables have their identity values set to match your interval lower bounds.</p> <p>Then, for every request you'd make an insert into the appropriate table and use <a href="http://technet.microsoft.com/en-us/library/ms177564.aspx" rel="nofollow">the OUTPUT clause</a> to get the newly generated identity value. </p> <p>For example, if the request was for a Red Card, you could write:</p> <pre><code>insert RedCardIds output inserted.Id default values </code></pre> <p>which would output:</p> <pre class="lang-none prettyprint-override"><code>Id ----------- 1 (1 row(s) affected) </code></pre> <p>On the next run it'll return <code>2</code>, and so on.</p> <p>Similarly, the first request for a Blue Card would trigger the statement:</p> <pre><code>insert BlueCardIds output inserted.Id default values </code></pre> <p>with the result:</p> <pre class="lang-none prettyprint-override"><code>Id ----------- 500001 (1 row(s) affected) </code></pre>

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