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POIdentity columns for multitenant database schemas
 

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  1. POIdentity columns for multitenant database schemas
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    <p>I'm creating a multitenant app where some of the tables need to have sequentially assigned integer values. The ordering is done independently for each tenant. As a concrete example, consider a <code>Student</code> table with a <code>RegNumber</code> column. <code>RegNumber</code> has to be assigned sequentially, but the sequence is local to each tenant.</p> <p>The solution I'm thinking of involves using another table to hold the "next available" <code>RegNumber</code> value for each tenant, which leads me to a couple of questions:</p> <ol> <li>Is there a better way?</li> <li>What is the best way to do a "SELECT FROM tenant_studentid_sequence" and "INSERT INTO students" in a single transaction without excessive locking, and without the possibility of skipping or duplicating values?</li> </ol> <p>In MySQL, I could use SELECT FOR UPDATE, but what about SQL Server 2008? There's quite a bit of discussion <a href="https://stackoverflow.com/questions/1483725/select-for-update-with-sql-server">on this SO question</a>, but it seems to be based on SQL Server 2005. Any changes in 2008? What's the recommended strategy?</p> <p><strong>Edit 1:</strong> I think I should clarify what I meant by "independently for each tenant". What I'm looking for is a way for each tenant to have a sequentially ordered set of student IDs. That is, tenant A will have students with IDs 1, 2, 3, ..., and so will tenant B. Think of them as business keys. I have GUIDs for global identity which is hidden from the customer.</p>
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      1. USGennady Vanin Геннадий Ванин
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    1. COIs there a reason that you can't use an identity column for this?
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    2. COI've edited the question to makes things a little clearer. An identity column would not allow me to have independent sequences for each tenant. I need tenants A and B to have instances of students with IDs 1, 2, 3, ...
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    3. COThis is the kind of requirement that needs to be pushed back. It is expensive to create a good solution for this and hard to properly maintain and utterly useless. Why do they need to have the same numbers per client? Utterly pointless 99.9% of the time. It is a waste of the clients' money to do this.
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