text: --+ holdcas on;
  ---- ALTER TABLE ...  CHANGE COLUMN  
  -- constraints : testing add/drop : NOT NULL, 
  -- ordering : no order defined
  -- name : same of different
  -- type : nchar , not type change 
  -- other :
  
  
  -- adding 'not null'  : strict mode
  set system parameters 'alter_table_change_type_strict=yes';
  
  
  create table t1 ( s1 nchar(10) );
  insert into t1 values (n'1234567890'),(n''),(NULL),(n'123'),(n'12 ');
  select s1, length(s1) from t1 order by 1;
  show columns in t1;
  
  alter table t1 change s1 s nchar(11) not NULL;
  
  select s1, length(s1) from t1 order by 1;
  
  show columns in t1;
  
  -- should fail:
  insert into t1 values (NULL);
  
  insert into t1 values ('12345678901');
  
  drop table t1;
  
  
  -- adding 'not null'  : permissive mode
  set system parameters 'alter_table_change_type_strict=no';
  set system parameters 'error_log_level=warning';
  set system parameters 'error_log_warning=yes'; 
  
  create table t1 ( s1 nchar(10) );
  insert into t1 values (n'1234567890'),(n''),(NULL),(n'123'),(n'12 ');
  select s1, length(s1) from t1 order by 1;
  show columns in t1;
  
  alter table t1 change s1 s nchar(11) not NULL;
  
  select s, length(s) from t1 order by 1;
  show columns in t1;
  
  -- should fail:
  insert into t1 values (NULL);
  
  insert into t1 values (n'12345678901');
  
  drop table t1;
  
  
  
  -- adding 'not null'  : permissive mode , but no existing NULL -> no warning
  set system parameters 'alter_table_change_type_strict=no';
  set system parameters 'error_log_level=warning';
  set system parameters 'error_log_warning=yes'; 
  
  create table t1 ( s1 nchar(10) );
  insert into t1 values (n'1234567890'),(n''),(n'123'),(n'12 ');
  select s1, length(s1) from t1 order by 1;
  show columns in t1;
  
  alter table t1 change s1 s nchar(11) not NULL;
  
  select s, length(s) from t1 order by 1;
  show columns in t1;
  
  -- should fail:
  insert into t1 values (NULL);
  
  insert into t1 values (n'12345678901');
  
  drop table t1;
  
  set system parameters 'alter_table_change_type_strict=no';
  
  commit;
  --+ holdcas off;
  