title: How to SELECT a PROCEDURE in Firebird 2.5
body: <p>I'm using Firebird Embedded v2.5. How to use procedures in query (SELECT) ?</p>
  
  <p>My procedure:</p>
  
  <pre class="lang-sql prettyprint-override"><code>SET TERM ^ ;
  CREATE PROCEDURE FN_TEST( Y INTEGER )
  RETURNS( X INTEGER)
  AS
  BEGIN
  X = Y + 1;
  END^
  SET TERM ; ^
  </code></pre>
  
  <p>I want to list some field of table modified by some procedure, like this:</p>
  
  <pre class="lang-sql prettyprint-override"><code>SELECT some_table_field_1, 
         fn_test( 4 ) AS zzz, 
         some_table_field_2,
         fn_test( some_table_field_2 ) AS field_2_modified
  FROM   tb_test
  </code></pre>
  
  <p>Need results (table):</p>
  
  <pre><code>some_table_field_1     zzz         some_table_field_2      field_2_modified
  ---------------------------------------------------------------------------
  aaa                    5           14                      15
  bbb                    5           23                      24
  www                    5           75                      76
  </code></pre>
  
  <p>This thing works fine in PostgreSQL, but I don't know how to do this in Firebird.</p>