sql server - How to set default value to existing rows while adding new column with default value to table -

i have table 100 rows , adding new column default value show below.

alter  table accountdetails add        updatedon      datetime    default getdate(),    updatedby      varchar(50) default 'system' 

after execution of alter statement new columns added table ... perfect! values existing rows these columns null.

is there anyways have default value default instead of executing separate update statement column update default value explicitly?

alter table {tablename}  add {columnname} {type} {null|not null}  constraint {constraint_name} default {default_value} [with values]