(Photo: Monta driving by Yogma)

Specifying one-to-many relationships is ridiculously easy in Ruby on Rails.  Unfortunately it’s not so straight-forward in ATG repositories.

First you specify the “belongs to” relationship.  In this example the player belongs to a team.

[xml]<item-descriptor name="player">
<table name="team_players" type="auxiliary" id-column-names="team_id" shared-table-sequence="1">
<property name="team" column-name="team_id" item-type="team" />
</table>
</item-descriptor>[/xml]

Then you specify the “has many” relationship.  In this example the team has many players.

[xml]<item-descriptor name="team">
<table name="team_players" type="multi" id-column-names="player_id" shared-table-sequence="2">
<property name="players" column-name="player_id" data-type="set" component-item-type="player" />
</table>
</item-descriptor>[/xml]

Note the trick is specifying the “shared-table-sequence.”

Here is the SQL for the table that specifies this relationship in our example.

[sql]CREATE TABLE team_players
(
team_id VARCHAR2(40) NOT NULL,
player_id VARCHAR2(40) NOT NULL,
CONSTRAINT team_players_pk PRIMARY KEY (team_id, player_id),
CONSTRAINT team_players_players_fk foreign key (player_id) references players (id),
CONSTRAINT team_players_team_fk foreign key (team_id) references teams (id)
);[/sql]