Need SQL Query improved for multiple column joins

I have this query

UPDATE Table1  
SET
      CompareFlag = 'Y'
WHERE
      (Table1.doc_id IN
      (
          SELECT Table2.doc_id
          FROM   Table2
          WHERE  (batch_id IS NULL)
      ));


there are two columns in Table1  one and Table2 two that need to be equal

Doc_ID and ObjectID  are in both tables.   So the Table1.doc_id IN (select will not work)

Thanks