title: Update table values from another table with the same user name
body: <p>I have two tables, with a same column named <code>user_name</code>, saying <code>table_a</code>, <code>table_b</code>.</p>
  
  <p>I want to, copy from <code>table_b</code>, <code>column_b_1</code>, <code>column_b2</code>, to <code>table_b1</code>, <code>column_a_1</code>, <code>column_a_2</code>, respectively, where the <code>user_name</code> is the same, how to do it in SQL statement?</p>