title: How to force update a DB grid?
body: <p>I may have been too clever for my own good :-/</p>
  
  <p>I have a table which holds some pressure measurements. These are always stored as PSI, but the user can select a radio group button to toggle between PSI and BAR.</p>
  
  <p>In order to keep the code clean and and push work onto the database, I created a second table for <code>configuration</code> items, with a single row. One column <code>psi_bar_conversion</code> will take the value either 1 or 14.5 as the user toggles the radio group.</p>
  
  <p>In Delphi, my query which ties to my DB grid is set up with statements like  </p>
  
  <pre><code>SELECT ROUND(inlet_waterPressure_psi  /  
                    (SELECT psi_bar_conversion FROM configuration), 
               (SELECT float_precision FROM configuration))
         AS inlet_waterPressure, 
  FROM measurements
  </code></pre>
  
  <p>All of which works just fine (and perhaps I am explaining too much).</p>
  
  <p>All that I am tring to do is add some code in the function which handles the radio button toggle to force my DB grid to refresh its contents becuase I have just updated the value of <code>configuration.psi_bar_conversion</code> (but no direct field of my query, nor of my datasource).</p>
  
  <p>Should I invoke <code>Refresh()</code> or <code>Invalidate()</code> or <code>SomeOtherFunction()</code> - of the DB grid, the query, the datasrouce?  That's what is confusing me.</p>
  
  <p>Thanks in advance for any help ....</p>