SQL Server中的时间范围仅适用于日期

我有一个名为Name的表Transactions，它包含这样的数据：

transaction_id   cust_id   tran_date  
 80712190438     270351     28-02-14
 29258453508     270384     27-02-14
 58387181112     275068     31-12-13
 21300411973     274568     31-12-13
 26229626485     267624     31-12-12
 26229126485     267634     31-12-12
 47557596721     273764     31-12-11
 28966519600     273899     31-12-11

现在，可用于分析的交易数据的时间范围是多少？

问题的第二部分是：

显示在输出number of Days，Months并Years同时进行。

两者都应在“单个查询”中完成。

我使用下面的查询来获取天，月和年，但是我一直在寻找时间范围。

SELECT 
    MIN(CAST(CAST(tran_date AS NCHAR(8)) AS date)) AS Start_tran_Date
    ,MAX(CAST(CAST(tran_date AS NCHAR(8)) AS date)) AS End_tran_Date
    ,DATEDIFF(DAY,MAX(CAST(CAST(tran_date AS NCHAR(8)) AS date)), MIN(CAST(CAST(tran_date AS NCHAR(8)) AS date)) ) AS Difference_Days
    ,DATEDIFF(MONTH,MAX(CAST(CAST(tran_date AS NCHAR(8)) AS date)), MIN(CAST(CAST(tran_date AS NCHAR(8)) AS date)) ) AS Difference_Months
    ,DATEDIFF(YEAR,MAX(CAST(CAST(tran_date AS NCHAR(8)) AS date)), MIN(CAST(CAST(tran_date AS NCHAR(8)) AS date)) ) AS Difference_Years
FROM Transactions

但这给了我这个错误：

消息241，级别16，状态1，第50行从字符串转换日期和/或时间时转换失败。

我想要输出

tran_date_start  tran_date_end  No.of Days  No.of Months  No.of Years