create procedure xs_delete
     @jszh char(8),@flag int output
as 
       if exists(select* from zzyxs where 借書證號=@jszh and 借書量=0)
          begin
               delete
                  from zzyxs
                  where   借書證號=@jszh and 借書量=0
             set @flag=0
          end
       else
           set @flag=1