I don't think you need a mapping table for one-to-many.
create table types (
type_id integer not null primary key
);
create table content (
content_id integer not null primary key
type_id integer not null references types
);
insert into types values (1);
insert into types values (2);
insert into content values (1,1);
insert into content values (2,1);
Now there is a one-to-many relationship beteen content and types, or a many-to-one relationship beteen types and content.
If you wanted to categorize the content, you might have a table of categories:
create table categories (
category_id integer not null primary key
category varchar(32) not null unique
);
insert into categories values (1,'good');
insert into categories values (2,'bad');
insert into categories values (3,'ugly');
-- and a mapping table:
create table content_category_map (
content_id ...
category_id ...
constraint ccm_un unique (content_id,category_id)
);
insert into content_category_map values (1,1);
insert into content_category_map values (1,2);
insert into content_category_map values (2,1);
insert into content_category_map values (2,2);
Now you have a many-to-many relationship between content and categories.
You can enforce a mapping table to be one-to-many by setting a unique constraint on one of the columns.
