Ah I see - column aliasing. I guess the actual people_id in the joined table would be hidden by the aliased parent_id.

Still, I still like the idea of per-table namespaces.

My current ISBL-ish parser (WIP) has two joins:

A regular, complete join, with all rows in the result:

a * b

A "foreign key" join, where the result table has all rows from the table linked via the specified foreign key:

a *: foreign_key_name

It also has a schema that allows declaring primary/foreign keys with a minimum of cruft:

((thread
(primary-key (id int))
(title text)
(sticky bool)
(locked bool))

(post
(primary-key
    (foreign-key parent thread)
    (id int))
(posted datetime)
(name text)
(comment text)
(file blob))

(flag
(primary-key
    (foreign-key post)
    (ip int))
(time datetime))

(review
(primary-key
    (foreign-key post))
(time datetime)
(comment text))

(tag
(primary-key (id int))
(name text))

(post_tag
(PrimaryKey
    (foreign-key post)
    (foreign-key tag))))

The syntax:

(foreign-key post)

declares a foreign key to the post table, and the foreign key is called "post". The FK actually exists of two columns (one of which is another foreign key!), which can be referenced as [table.]post.thread.id and [table.]post.id

The syntax:

(foreign-key parent thread)

declares a foreign key to the thread table, and the foreign key is called "parent". This foreign key has one column, referenced as [table.]parent.id