I need to have the value of the column as the current date what is the query to set the value as the current date.

select current date from sysibm.sysdummy1
is that what you mean or pleae, be more specific

update emp set birthdate = current_date;

or

update emp set birthdate = current_date where birthdate is null;

Note sure which of the above you want.

I you want the current date to be the default going forward for newly inserted rows, you can alter the table to set the default value for the column to current_date.