title: Update Microsoft SQL Server value without unique key
body: <p>I am working on creating a front end for a role access management program. I need to figure out how to update a <code>userName</code> that does not have a unique value. Also in the table it has a <code>loweredUserName</code> column.  </p>
  
  <p>Here is my SQL statement:</p>
  
  <pre><code>UPDATE mssql_Users
  SET UserName = @UserName,
      LoweredUserName = LOWER(@UserName)
  WHERE UserName = @UserName
  </code></pre>
  
  <p>So basically if there are multiple versions of the user name <code>'testUser'</code>  I want to replace every instance of <code>'testUser'</code> with the new name of say <code>'userTest'</code> without having any other unique id</p>