CREATE TABLE categories (
    id          INTEGER PRIMARY KEY AUTOINCREMENT,
    site_id     INTEGER NOT NULL,
    guid        TEXT    NOT NULL,
    name        TEXT    NOT NULL,
    slug        TEXT    NOT NULL,
    description TEXT    NOT NULL DEFAULT '',
    created_at  INTEGER NOT NULL,
    updated_at  INTEGER NOT NULL,
    FOREIGN KEY (site_id) REFERENCES sites (id) ON DELETE CASCADE
);
CREATE INDEX idx_categories_site ON categories (site_id);
CREATE UNIQUE INDEX idx_categories_guid ON categories (guid);
CREATE UNIQUE INDEX idx_categories_site_slug ON categories (site_id, slug);

CREATE TABLE post_categories (
    post_id     INTEGER NOT NULL,
    category_id INTEGER NOT NULL,
    PRIMARY KEY (post_id, category_id),
    FOREIGN KEY (post_id) REFERENCES posts (id) ON DELETE CASCADE,
    FOREIGN KEY (category_id) REFERENCES categories (id) ON DELETE CASCADE
);
CREATE INDEX idx_post_categories_category ON post_categories (category_id);