text: CREATE TABLE tst_helper (i int);
  insert into tst_helper values (11),(12),(13),(14);
  CREATE TABLE tst (int_col int, string_col string default 'user');
  insert into tst(int_col) values (1);
  select * from tst;
  ALTER TABLE tst CHANGE COLUMN string_col string_col string default user();
  insert into tst(int_col) values (2);
  insert into tst values (3, DEFAULT);
  insert into tst(int_col) select i from tst_helper;
  select if (lower(substring_index(string_col,'@',1)) = lower(substring_index(user(),'@',1)), 'ok', 'nok') from tst where string_col is not null;
  ALTER TABLE tst CHANGE COLUMN string_col string_col string default 'user';
  insert into tst(int_col) values (22);
  insert into tst values (23, DEFAULT);
  insert into tst(int_col) select i+15 from tst_helper;
  select * from tst where int_col > 20 order by int_col;
  drop table tst_helper;
  drop table tst;
  