--> 测试数据：[test]
if object_id('[test]') is not null drop table [test]
create table [test]([typeName] varchar(6),[theDate] datetime)
insert [test]
select '哈密瓜','2012-03-01' union all
select '雪莲','2012-03-08' union all
select '西瓜','2012-03-13'


select [typeName],[theDate] from(
select *,
DATEADD(mm,3,[theDate]) as enddate from test)t
where enddate>='2012-05-26' and [theDate] between '2012-04-27' and '2012-05-26'

------解决方案--------------------

你给的条件中，其实5月26号就根本没有用了，只要保质期大于4月27号就都属于这个范围内的。。。
SQL code

IF EXISTS (SELECT 1 FROM SYSOBJECTS WHERE name = 'tba')
BEGIN
    DROP TABLE tba
END
GO
CREATE TABLE tba
(
    typeName VARCHAR(100),
    theDate VARCHAR(100)
)

INSERT INTO tba
SELECT '哈密瓜', '2012-03-01' UNION
SELECT '雪莲', '2012-03-08' UNION
SELECT '西瓜', '2012-03-13' UNION
SELECT '美人瓜','2012-4-25'

--4.27-5.26

SELECT * FROM tba
WHERE DATEADD(MONTH,3,theDate) > '2012-04-27'

typeName    theDate
哈密瓜    2012-03-01
美人瓜    2012-4-25
西瓜    2012-03-13
雪莲    2012-03-08