sql - Update datetime column by one minute for few rows having same datetime -

i have table lots of data:

+----+-------+-------------------------+ | id | user  |        datetime         | +----+-------+-------------------------+ |  1 | 34534 | 2015-08-12 10:03:22.043 | |  2 | 32423 | 2015-08-12 03:29:18.097 | |  3 | 12312 | 2015-08-13 03:24:10.073 | |  4 | 34232 | 2015-08-13 03:24:10.073 | |  5 | 32462 | 2015-08-13 03:24:10.073 | |  6 | 45354 | 2015-08-14 04:12:04.023 | +----+-------+-------------------------+ 

i want create 1 minute gap between datetime of rows same. in above case, row number 3,4,5. 1 minute gap in these 3 datetime.

try this

select id,        user,        [datetime] = case when rn = 1 [datetime] else dateadd(minute,rn-1,[datetime]) end ( select row_number()over(partition [datetime] order id) rn,* yourtable ) 

for updating table use this

with cte ( select row_number()over(partition [datetime] order id) rn,* yourtable )  update cte set [datetime] =  case when rn = 1 [datetime] else dateadd(minute,rn-1,[datetime]) end