ksqldb updating with null values in insert statement

Question

I am trying to insert some values into a stream as follows:

ksql> create stream test(id bigint key, col1 varchar, col2 varchar) with(kafka_topic='test', partitions=3, value_format='json');

 Message        
----------------
 Stream created 
----------------
ksql> insert into test(id, col1) values(2, 'hey');
ksql> insert into test(id, col1) values(2, 'hello');
ksql> insert into test(id, col2) values(2, 'Hii');
ksql> select * from test;
+-----------------------------------------------------------------+-----------------------------------------------------------------+-----------------------------------------------------------------+
|ID                                                               |COL1                                                             |COL2                                                             |
+-----------------------------------------------------------------+-----------------------------------------------------------------+-----------------------------------------------------------------+
|2                                                                |hey                                                              |null                                                             |
|2                                                                |hello                                                            |null                                                             |
|2                                                                |null                                                             |Hii       

upon inserting the third entry, the col1 becomes null but this is not the value that I inserted. I just inserted into col2. Is there a way to not override other columns with null when it is not requested in insert?

Thank you.