Insert into an Oracle table only if it does not already exist (no errors)

insert_if_not_exsits.sql

-- first SELECT has values you want to insert.
-- second SELECT has enough of those values to verify if record already exists (e.g. primary key)
insert into some_table(col1, col2) 
	select "value 1", "value 2" from dual where not exists 
		(select 1 from some_table where col1 = "value 1" and col2 = "value3")