text: --+ holdcas on;
  ---- ALTER TABLE ...  CHANGE COLUMN  , type change
  -- constraints : no constraints
  -- ordering : no order defined
  
  set system parameters 'alter_table_change_type_strict=no';
  set system parameters 'error_log_level=warning';
  set system parameters 'error_log_warning=yes';
  
  -------------- varnchar 1 : to date, contains incompatible chars
  create table t1 (s1 nchar varying(20));
  insert into t1 values (n'2010-10-10'),(n'abc');
  
  select * from t1 order by 1;
  show columns in t1;
  
  -- should fail
  alter table t1 change s1 d1 date;
  
  insert into t1 values (n'123');
  
  --select * from t1 order by 1;
  select substring(d1,1,5) from t1 order by 1;
  show columns in t1;
  
  drop table t1;
  
  
  -------------- varnchar 2 : to date, contains only compatible chars
  create table t1 (s1 nchar varying(20));
  insert into t1 values (n'2010-10-10'),(n'2000-03-01');
  
  select * from t1 order by 1;
  show columns in t1;
  
  -- should fail
  alter table t1 change s1 d1 date;
  
  insert into t1 values (n'123');
  
  --select * from t1 order by 1;
  select substring(d1,1,5) from t1 order by 1;
  show columns in t1;
  
  drop table t1;
  commit;
  --+ holdcas off;
  
  set system parameters 'error_log_level=syntax';
  set system parameters 'error_log_warning=no';
  
  