title: T-SQL DecryptByKey returns NULL with Column Value, but not with Column Name
body: <p>I have an encrypted varbinary(MAX) field in my DB called ACCT_FName_encrypt. </p>
  
  <p>I can successfully decrypt this field with: </p>
  
  <pre><code>CONVERT(nvarchar(MAX), DecryptByKey(ACCT_FName_encrypt)) AS 'ACCT_FName_Denc'
  </code></pre>
  
  <p>But if I try to decrypt the actual value from the column, I get NULL: </p>
  
  <pre><code>CONVERT(nvarchar(MAX), DecryptByKey('0x001D25D87D3D8E49A97863ADC4958E790100000021E26DD2305384AE49EC9329EF2AF8758134F7C946EC9FE024805B8DF21472C4545D461DA9F2B7F96094C2AED09BF4A9')) AS 'ACCT_FName_Denc'
  </code></pre>
  
  <p>How can I get the decrypted value from the straight varbinary, without calling the field?</p>