title: Update rows in one table with data from another table based on one column in each being equal
body: <p>Update <em><strong>many rows</strong></em> into one table from another table based on one column in each being equal (user_id).</p>
  <p>both tables have a <code>user_id</code> column. Need to insert data from <code>t2</code> into <code>t1</code> when the <code>user_id</code> column are equal.</p>