text: --[er]Test function nullif with different data type
  
  Create class t1(a date, b date, c timestamp);
  insert into t1 values(DATE '05/09/2008', null, TIMESTAMP '05/09/2008 21:18:00');
  insert into t1 values(DATE '05/10/2008', DATE '05/09/2008', TIMESTAMP '05/09/2008 9:00:00');
  insert into t1 values(DATE '05/09/2008', DATE '05/09/2008', TIMESTAMP '05/09/2008 11:00:01');
  insert into t1 values(NULL, DATE '05/09/2008', NULL);
  insert into t1 values(DATE '05/10/2008', DATE '05/09/2008', NULL);
  
  
  select nullif(b,c)) from t1;
  select nullif(a,c)) from t1;
  select nullif(a,b)) from t1 where a is null;
                        
  
  drop table t1;
  