Point at correct all_from file

[dbsrgits/DBIx-Class-Manual-SQLHackers.git] / NOTES.txt

## Removed from UPDATE.pod:

=head2 Update a row or rows using a column calculation

    -- Yet another pointless example
    UPDATE users
    SET username = username || '.uk'
    WHERE id = 1;

=over

=item 1. Create a Schema object representing the database you are working with:

        my $schema = MyDatabase::Schema->connect('dbi:SQLite:my.db');

=item 2. Call the B<find> method on the resultset for the L<ResultSource|DBIx::Class::ResultSource> you wish to fetch data from:

        my $fred_user = $schema->resultset('User')->find({ id => 1 });

The Row object has an B<update> method that will change the values on
the object, and send an UPDATE query to the database.

=item 3. Call the B<update> method, passing it a hashref of new data:

# this won't yet work, DBIC for now mandates the [ {} => $value ] format, the simple \[ $sql, $value1, $value2 ] will start being recognized later on 
# the only documentation we currently have is this, if you can turn it into a DBIC pod-patch it will be freaking awesome
# https://github.com/dbsrgits/dbix-class/commit/0e773352
        $fred_user->update({ username => \['username || ?', '.uk'] }); 

^^ you never got around to this

# the DBIC syntax is a tad different from te thing above (i.e. we no longer encourage 'dummy' crap)
The \[ .. ] syntax here is described in L<SQL::Abstract>
documentation, used for passing bind parameters.


=back

=head2 Update a row based on data in other tables

    -- Slightly less pointless example
    UPDATE posts 
    SET title = user.username || title
    JOIN users user ON user.id = posts.user_id;

Joining two tables for an update is a similar sort of exercise to
joining them for a select query and using data from both.

=over

=item 1. Create a Schema object representing the database you are working with:

        my $schema = MyDatabase::Schema->connect('dbi:SQLite:my.db');

=item 2. Call the B<search> method on the resultset for the L<ResultSource|DBIx::Class::ResultSource> you wish to update data in, joining to the second table:

        my $posts = $schema->resultset('Post')->search(
          {},
          { join => 'user' }
        );

    The B<join> key takes as an argument a nested structure of one or more relation names (see L<DBIx::Class::Manual::SQLHackers::CREATE>).

=item 3. Call the B<update> method on the resultset to run the UPDATE statement:

        $posts->update({ 'me.title' => \[ 'user.username || me.title' ] });

^^ I am 95% sure this won't actually work, please try it (ideally as a passing or failing test)

=back