怎么判断字符的长度

如何判断字符的长度
select * from x_user where and datediff(day,getdate(),isnull(user_time,'3000-12-31'))>1
如何变成当user_time的长度小于5时，则是'3000-12-31'

[解决办法]

SQL code

select * from x_user where and datediff(day,getdate(),(case when len(user_time)<5 then '3000-12-31' else user_time end)))>1
[解决办法]
SQL code
SELECT CASE            WHEN LEN(user_time) < 5           THEN '3000-12-31'           ELSE ''        END
[解决办法]
SQL code
SELECT  *FROM    x_userWHERE   DATEDIFF(day, GETDATE(), CASE WHEN LEN(user_time) < 5 THEN '3000-12-31'                                      ELSE ''                                 END) > 1
[解决办法]
SQL code
SELECT  CASE WHEN LEN(user_time) < 5 THEN '3000-12-31'                                      ELSE ''                                 END,*FROM    x_userWHERE   datediff(day,getdate(),isnull(user_time,'3000-12-31'))>1
[解决办法]
SQL code
select (case when len(user_time)<5 then '3000-12-31' else user_time end) usertime from x_user where and datediff(day,getdate(),usertime))>1