select a.ID,a.Name,a.ClassID,t.value
from A a inner join(
select  Number,Value,State from(
select 
px=row_number()over(partition by Number order by Value),* 
from B where State=0)s where px=1)t
on t.Number=a.ID

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

IF EXISTS (SELECT 1 FROM SYSOBJECTS WHERE name = 'A')
BEGIN
    DROP TABLE A
END
GO
CREATE TABLE A
(
    ID VARCHAR(10),
    Name VARCHAR(10),
    Address VARCHAR(10),
    ClassID VARCHAR(10)
)
GO
INSERT INTO A
SELECT '1-1', '张三', '武汉', '0123' UNION
SELECT '1-2', '王五', '长沙', '0123'

IF EXISTS (SELECT 1 FROM SYSOBJECTS WHERE name = 'B')
BEGIN
    DROP TABLE B
END
GO
CREATE TABLE B
(
    Number VARCHAR(10),
    Value INT,
    State INT
)
GO
INSERT INTO B
SELECT '1-1', 2, 0 UNION
SELECT '1-1', 3, 0 UNION
SELECT '1-2', 2, 1

GO

SELECT ID,Name,ClassID,Value
FROM A,(SELECT Number,MIN(value) AS value FROM B WHERE State = 0 GROUP BY Number) AS C
WHERE A.ID = C.Number

ID    Name    ClassID    Value
1-1    张三    0123    2

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

if object_id('[tb_A]') is not null drop table [tb_A]
create table [tb_A]
insert  [tb_A]
SELECT '1-1', '张三', '武汉', '0123' UNION ALL
SELECT '1-2', '王五', '长沙', '0123'


if object_id('[tb_B]') is not null drop table [tb_B]
create table [tb_B]
INSERT  [tb_B]
SELECT '1-1', 2, 0 UNION ALL
SELECT '1-1', 3, 0 UNION ALL
SELECT '1-2', 2, 1

SELECT ID,Name,ClassID,Value
FROM tb_A,(SELECT Number,MIN(value) AS value FROM tb_B WHERE State=0 GROUP BY Number) AS tb_C
WHERE tb_A.ID = tb_C.Number

ID     Name    ClassID    Value
1-1    张三     0123        2