关于DateTime类型和Date类型比较时的困惑

CREATE TABLE T_TEST(ID INT IDENTITY PRIMARY KEY,CreateTime DATE)
INSERT INTO T_TEST SELECT '2011-11-04'
UNION ALL SELECT '2011-11-04'
UNION ALL SELECT '2011-11-04'
UNION ALL SELECT '2011-11-05'
UNION ALL SELECT '2011-11-05'
UNION ALL SELECT '2011-11-05'

SELECT * FROM T_TEST

SELECT COUNT(*) FROM T_TEST 
WHERE  CreateTime>='2011-11-04 00:00:00' AND CreateTime <'2011-11-04 23:59:59'
--等价于(返回0行 不太明白????)

--传入参数为datetime类型(返回3行，这个可以理解，但和上面又有啥区别呢？不解)
SP_executesql N'
    select COUNT(*) 
    from T_TEST
    where CreateTime>=@BeginTime and CreateTime<@EndTime
',N'@BeginTime datetime,@EndTime datetime',
@BeginTime='2011-11-04 00:00:00',
@EndTime='2011-11-04 23:59:59'    

--修改了传参类型为date类型(返回0行，这个也可以理解)
SP_executesql N'
    select COUNT(*) 
    from T_TEST
    where CreateTime>=@BeginTime and CreateTime<@EndTime
',N'@BeginTime date,@EndTime date',
@BeginTime='2011-11-04 00:00:00',
@EndTime='2011-11-04 23:59:59'

--又看下面的例子
DECLARE @EndTime datetime
 SET @EndTime='2011-11-04 23:59:59' 
DECLARE @CreateTime DATE
 SET @CreateTime='2011-11-04' 

IF @CreateTime<@EndTime  --打印出来，可以理解，但为啥前面的不对呢？
 PRINT '@CreateTime<@EndTime'