title: SQL how to encrypt nvarchar column
body: <p>I have the following code (<code>SQL server 2014</code>):</p>
  
  <pre><code>    declare @f nvarchar(10) = 'فيدف '
      update mytable set mycol=ENCRYPTBYPASSPHRASE('key', @f) where id = 1
  
      declare @encrypt varbinary(750) 
      select @encrypt = (select mycol from mytable where id =1)
  
      select  convert(nvarchar(255),DECRYPTBYPASSPHRASE('key',@encrypt))
  </code></pre>
  
  <p>The result of the decryption is '??????', why is this?</p>