Extracting valid timestamps in SQL

I am working with Netezza sql. I have a table (my_table). For col_1, I only want to extract rows that are in the following format: 2020-01-01 12:00:00 and col_2 is only numbers

I am trying to do this with regexp_extract:

SELECT *
FROM my_table
WHERE regexp_extract(col_1, 
                     '^[0-9]{4}-[0-9]{2}-[0-9]{2} [0-9]{2}:[0-9]{2}:[0-9]{2}$') 
      IS NOT NULL;

SELECT *
FROM my_table
WHERE regexp_like(col_2, '^[0-9]+$');

Is there a more uniform way to do this such that it can work on multiple different versions of SQL? I.e. perhaps some versions of sql do not have the regexp_extract command

See simple example

SELECT t.*
  ,translate(col_1,'0123456789','9999999999') c1
  ,replace(translate(col_2,'0123456789','9999999999'),'9','') c2
FROM test t
where not( 
        (translate(col_1,'0123456789','9999999999')='9999-99-99 99:99:99')
    and (replace(translate(col_2,'0123456789','9999999999'),'9','')='')
  )
;

fiddle