select * from b where id <> (select id from b inner join c on b.ContractNO=c.ContractNO and b.Supplier
=c.Supplier
)

------解决方案--------------------
SQL code
select b.* from b left join c on b.ContractNO=c.ContractNO and b.Supplier
=c.Supplier
where c.ContractNO is null

------解决方案--------------------
SQL code


create table tA
(
  ID int,
  ContractNO varchar(5),
  Product nvarchar(10),
  Supplier nvarchar(10)
)

insert into tA
select 1,'11111', '卷尺', '上海'  union all
select 2, '11111', '橡皮', '北京'  union all
select 3, '11111', '卷尺', '北京'  union all
select 4, '22222', '卷尺', '上海'  union all
select 5, '33333', '卷尺', '上海'

create table tB
(
  ID int,
  ContractNO varchar(5),
  Supplier nvarchar(10)
)

insert into tB
select 1,'11111','北京'  union all
select 2, '33333',  '上海' 

select * from tA a where not exists(select 1 from tB where ContractNO=a.ContractNO and Supplier=a.Supplier)

------解决方案--------------------
SQL code
select b.* from b right join c on b.ContractNO=c.ContractNO and b.Supplier
=c.Supplier
where b.ContractNO is null

------解决方案--------------------
SQL code

if object_ID('b') is not null
   drop table b
go
create table b
(
 id int identity(1,1),
 contractno varchar(10),
 product varchar(10),
 supplier varchar(10)
)
go
insert into b (contractno,product,supplier)
select '11111','卷尺','上海' union all
select '11111','橡皮','北京' union all
select '11111','卷尺','北京' union all
select '22222','卷尺','北京' union all
select '33333','卷尺','上海'
go
if object_id('c') is not null
   drop table c
go
create table c
(
 id int identity(1,1),
 contractno varchar(10),
 supplier varchar(10)
)
go
insert into c (contractno,supplier)
select '11111','北京' union all
select '33333','上海'
go
select * from b t1 where not exists(select 1 from c where contractno=t1.contractno and Supplier=t1.Supplier)
/*
id          contractno product    supplier
----------- ---------- ---------- ----------
1           11111      卷尺         上海
4           22222      卷尺         北京

(2 行受影响)
*/