Stored Pocedure

How can I execute all the three sql statments below in single stored procedure?  if the first statement is returned no row, then only I want to execute the second and third statments.

SELECT a.* FROM Table1 a INNER JOIN Table2 b
            ON a.PartNo = b.PartNo and a.StoreID = b.StoreID Where b.QtyIn > 
            a.Stock and b.Id=@Id

       UPDATE Table1 SET Stock = P.Stock - PI.QtyIn from
            Table1 as P Inner Join Table2 as PI on P.PartNo=PI.PartNo and
            P.StoreID = PI.StoreID WHERE PI.Id=@Id

       delete from Table2 where Id=@id

thanks

ayha