title: In SQL Server can I index on an "AS" column?
body: <p>I have this table:</p>
  
  <pre><code>CREATE TABLE [dbo].[Kanji] 
  (
      [KanjiId] UNIQUEIDENTIFIER DEFAULT (newid()) NOT NULL,
      [Text] NVARCHAR(5) NOT NULL,
      [Freq] INT NULL,
      [Grade] INT NULL,
      [Hash] AS (CONVERT([bigint], hashbytes('md5', [Name])) % (5) + (5)),
  }
  </code></pre>
  
  <p>I would like to index by <code>Text</code> and then <code>Hash</code>. But is it possible with a column that is computed with an <code>AS</code> expression? And if so are there performance issues I should consider?</p>