sergey@comp:~$ sqlite3 test_guru
sqlite> create table categories(id integer primary key autoincrement, title varchar(30));
sqlite> create table tests(id integer primary key autoincrement, title varchar(30), level integer, categories_id integer not null, foreign key (categories_id) references categories(id));
sqlite> create table questions (
   ...> id integer primary key autoincrement,
   ...> body text,
   ...> tests_id integer not null,
   ...> foreign key (tests_id) references tests(id)
   ...> );
sqlite> insert into categories(title) values
   ...> ('HTML'),
   ...> ('CSS'),
   ...> ('RUBY');
sqlite> insert into tests(title, level, categories_id) values
   ...> ('Basic html', 0, 1),
   ...> ('Basic css', 0, 2),
   ...> ('Basic ruby', 0, 3),
   ...> ('Advanced ruby', 3, 3),
   ...> ('Average ruby', 2, 3);
sqlite> insert into questions(body, tests_id) values
   ...> ('That is html', 1),
   ...> ('That is css?', 2),
   ...> ('That is ruby?', 3),
   ...> ('That is exeption?', 5),
   ...> ('That is metaprogramming?', 4);
sqlite> select * from tests where level = 2 or level = 3;
4|Advanced ruby|3|3
5|Average ruby|2|3
sqlite> select * from questions where tests_id = 1;
1|That is html|1
sqlite> update tests
   ...> set title = 'Intermediate ruby', level = 2
   ...> where id = 4;
sqlite> delete from questions where tests_id = 4;
sqlite> select tests.title, categories.title
   ...> from tests
   ...> join categories
   ...> on tests.categories_id = categories.id;
Basic html|HTML
Basic css|CSS
Basic ruby|RUBY
Intermediate ruby|RUBY
Average ruby|RUBY
sqlite> select questions.body, tests.title
   ...> from questions
   ...> join tests
   ...> on questions.tests_id = tests.id;
That is html|Basic html
That is css?|Basic css
That is ruby?|Basic ruby
That is exeption?|Average ruby