title: sy-datum low and high definitions
body: <p>I have an ABAP program with below sample code which should select data from an SAP table based on a date column.</p>
  
  <pre><code>INITIALIZATION. 
  select-OPTIONS: so_date FOR sy-datum.  
  START-OF-SELECTION. 
  so_date-sign = 'I'. 
  so_date-option = 'BT'. 
  so_date-low = sy-datum. 
  so_date-high = '99991231'. 
  APPEND so_date.
  </code></pre>
  
  <p>and my select stmt is:</p>
  
  <pre><code>select c1,c2,c3 
  from &lt;sap_table&gt;
  where &lt;date_column&gt; in so_date.
  </code></pre>
  
  <p>I want to know the purpose of setting so_date-high = '99991231' and how it will behave.</p>