text: --+ holdcas on;
  -- null
  prepare s from 'select unix_timestamp (?) into :result';
  execute s using null;
  deallocate prepare s;
  
  evaluate unix_timestamp (null) into :expected;
  select case when :expected <=> :result then 'YES' else 'NO' end as case1;
  
  -- na
  prepare s from 'select unix_timestamp (?) into :result';
  execute s using na;
  deallocate prepare s;
  
  evaluate unix_timestamp (na) into :expected;
  select case when :expected <=> :result then 'YES' else 'NO' end as case2;
  
  
  --+ holdcas off;
  