SET NOCOUNT ON
DECLARE @object int
CREATE TABLE #load_result (ret_code int) 
DECLARE @hr int
DECLARE @src varchar( 8000 ), @count int
SET @src = '<root><el1><el2/></el1><el1><el2/><el2/></el1><el1><el2><el3/></el2></el1><el1><el2/><el2><el3/></el2></el1></root>'
EXEC @hr = sp_OACreate 'MSXML2.DOMDocument', @object OUT
IF @hr <>  0 
BEGIN
   EXEC sp_OAGetErrorInfo @object
    RETURN
END
INSERT INTO #load_result (ret_code)
EXEC @hr = sp_OAMethod @object, 'loadXML', null, @src
/* или так (тоже работает):
DECLARE @load_res int
EXEC @hr = sp_OAMethod @object, 'loadXML', @load_res OUT, @src
*/
IF @hr <>  0 
BEGIN
   EXEC sp_OAGetErrorInfo @object
    RETURN
END
EXEC @hr = sp_OAGetProperty @object, 'documentElement.childNodes.length', @count OUT
IF @hr <>  0 
BEGIN
   EXEC sp_OAGetErrorInfo @object
    RETURN
END
SELECT @count as el1_count
DROP TABLE #load_result