-- Lessons belong to a Module.
CREATE TABLE lessons (
    id BIGSERIAL PRIMARY KEY,
    module_id BIGINT NOT NULL REFERENCES modules (id) ON DELETE CASCADE,
    title VARCHAR(255) NOT NULL,
    video_url TEXT,
    thumbnail TEXT,
    description TEXT,
    created_at TIMESTAMPTZ NOT NULL DEFAULT CURRENT_TIMESTAMP,
    updated_at TIMESTAMPTZ
);

CREATE INDEX idx_lessons_module_id ON lessons (module_id);
CREATE INDEX idx_lessons_module_created ON lessons (module_id, created_at DESC);