Cross-list queries with SPSiteDataQuery

Scenario:
You need to query cross-list items across multiple Web sites

Solution:
'SPSiteDataQuery' is more efficent for such a situation.
'SPQuery' should be used to query a particular list

Sample Code:

SPWeb webSite = SPContext.Current.Web;
SPSiteDataQuery query = new SPSiteDataQuery();

query.Lists = "<Lists ServerTemplate=\"107\" />";
query.Query = "<Where><Eq><FieldRef Name=\"Status\"/>" +
   "<Value Type=\"Text\">Completed</Value></Eq></Where>";

System.Data.DataTable items = webSite.GetSiteData(query);

foreach (System.Data.DataRow item in items)
{
   Response.Write(SPEncode.HtmlEncode(item["Title"].ToString()) + "<BR>");
}