create procedure jy_insert
   @jszh char(8),@isbn char(16),@ssh char(10),@jssj datetime,@flag int output
 as
    set @flag=(select 庫存量 from zzybook where ISBN=@isbn)
    if @flag>0 
             begin
                 insert into zzyjy(借書證號,ISBN,索書號,借書日期)
                              values(@jszh,@isbn,@ssh,@jssj)
             end
    else 
         set @flag=0