method is similar to
inner_join() except that its output includes every
output of the left-hand query at least once. It's a wrapper for SQL's
For any queries
you can call
) provided that:
abstract_mapper<bool>(in practice it will be a
r's value type cannot be represented as all
NULLs (which is unlikely to arise, but see here for a discussion of which types allow all
mappers will both be visible
) returns a
with the following characteristics:
r's value types respectively.
>>, in which:
l's value mapper, and
>whose content mapper is identical to
r's value mapper.
std::tuples formed from each combination of the outputs of
r, for which
boost::none}, for each of
lothat would not have made an appearance otherwise.
const query<std::tuple<screen, boost::optional<movie>>> no_screen_left_behind = screens.left_join(movies, screens->current_movie_id == movies->id);