title: Update mysql table with select query from another database
body: <p>I have two databases and I want to update one table with values from another database table.
  I am using the following query but it does not work.</p>
  
  <pre><code>UPDATE database1.table1
  SET field2 = database2.table1.field2
  WHERE database1.table1.field1 = database2.table1.field1
  </code></pre>
  
  <p>I have also tried the following query but it does not work either:</p>
  
  <pre><code>UPDATE database1.table1
  SET field2 = "SELECT field2 FROM database2.table1"
  WHERE database1.table1.field1 = database2.table1.field1
  </code></pre>