CAML Designer support for SPSiteDataQuery
Yesterday we’ve put a new version of the CAML Designer online. This version introduces support for Site Data Queries. When you open the CAML Designer, you will see that there are 2 buttons on the ribbon now: one for CAML Query and one for Site Data Query. The CAML Query button is enabled by default.
You can execute site data queries with the server-side object model using SPSiteDataQuery. As there is no alternative for web services and client-side object model, this button is disabled when logging on other then with the server-side object model.
More detailed documentation on CAML and the CAML Designer can be found here.