title: How to pass a parameter to a query using dbExpress in Delphi
body: <p>I want to use a dbExpress TSQLQuery component. But i do not know how to write the SQL to add a parameter. I will give an example maybe it will be more clear what my problem is.</p>
  
  <p>In a TADOQuery the following works:</p>
  
  <pre><code>SELECT*
  FROM sometable
  WHERE sometable.id = :value;
  </code></pre>
  
  <p>Now in the above example you pass the parameter to the query using the colon (:) before the parameter name. But when I try and do that with the TSQLQuery, I get the following error:</p>
  
  <pre><code>dbExpress driver does not support the TDBXTypes.UNKNOWN data type. Vendor Error Message.
  </code></pre>
  
  <p>Now if this is not the way that you pass a parameter in a TSQLQuery component, can someone please assist me. This is new territory for me.</p>
  
  <p>Im using a Firebird database, and Im using Delphi XE2</p>