lemmy/migrations/2019-10-19-052737_create_user_mention/up.sql

CREATE TABLE user_mention (
    id serial PRIMARY KEY,
    recipient_id int REFERENCES user_ ON UPDATE CASCADE ON DELETE CASCADE NOT NULL,
    comment_id int REFERENCES COMMENT ON UPDATE CASCADE ON DELETE CASCADE NOT NULL,
    read boolean DEFAULT FALSE NOT NULL,
    published timestamp NOT NULL DEFAULT now(),
    UNIQUE (recipient_id, comment_id)
);

CREATE VIEW user_mention_view AS
SELECT
    c.id,
    um.id AS user_mention_id,
    c.creator_id,
    c.post_id,
    c.parent_id,
    c.content,
    c.removed,
    um.read,
    c.published,
    c.updated,
    c.deleted,
    c.community_id,
    c.banned,
    c.banned_from_community,
    c.creator_name,
    c.score,
    c.upvotes,
    c.downvotes,
    c.user_id,
    c.my_vote,
    c.saved,
    um.recipient_id
FROM
    user_mention um,
    comment_view c
WHERE
    um.comment_id = c.id;