title: Update a column in MySQL
body: <p>I have a table <code>table1</code> with three columns and a bunch of rows:</p>
  
  <pre><code>[key_col|col_a|col_b]
  </code></pre>
  
  <p>I want to update col_a with a set of values (i.e. leaving <code>col_b</code> unchanged), something like this:</p>
  
  <pre><code>INSERT INTO table1 AS t1 (key_col, col_a) VALUES ("k1", "foo"), ("k2", "bar");
  </code></pre>
  
  <p><br>
  But it doesn't work, how do I do this?</p>