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:

1. SPWeb webSite = SPContext.Current.Web;
2. SPSiteDataQuery query = new SPSiteDataQuery();
4. query.Lists = "";
5. query.Query = "" +
6. "Completed";
8. System.Data.DataTable items = webSite.GetSiteData(query);
10. foreach (System.Data.DataRow item in items)
11. {
12. Response.Write(SPEncode.HtmlEncode(item["Title"].ToString()) + "
    ");
13. }