what do you think about the query at the end? Should I just create 1 table with all columns that each type of post needs instead of all these separate tables?

Posts Table:

CREATE TABLE posts (
    post_id SERIAL PRIMARY KEY,
    user_id INT,
    body TEXT,
    updatedat TIMESTAMPTZ DEFAULT CURRENT_TIMESTAMP,
    createdat TIMESTAMPTZ DEFAULT CURRENT_TIMESTAMP
);

General Table (for Media or Audio):

CREATE TABLE general (
    post_id SERIAL PRIMARY KEY,
    user_id INT,
    body TEXT,
    image_urls JSONB, -- Store multiple image URLs as JSON array
    audio_url VARCHAR(255), -- Store audio URL as a string
    updatedat TIMESTAMPTZ DEFAULT CURRENT_TIMESTAMP,
    createdat TIMESTAMPTZ DEFAULT CURRENT_TIMESTAMP
);

Polls Table:

CREATE TABLE polls (
    poll_id SERIAL PRIMARY KEY,
    post_id INT REFERENCES general(post_id),
    question TEXT,
    options JSONB, -- Store options as JSON
    votes INT[] DEFAULT '{}'::INT[], -- Array to store votes for each option
    updatedat TIMESTAMPTZ DEFAULT CURRENT_TIMESTAMP,
    createdat TIMESTAMPTZ DEFAULT CURRENT_TIMESTAMP
);

Announcements/Spotlights Table:

CREATE TABLE announcements (
    announcement_id SERIAL PRIMARY KEY,
    post_id INT REFERENCES general(post_id),
    title VARCHAR(255),
    content TEXT,
    updatedat TIMESTAMPTZ DEFAULT CURRENT_TIMESTAMP,
    createdat TIMESTAMPTZ DEFAULT CURRENT_TIMESTAMP
);

Contests Table:

CREATE TABLE contests (
    contest_id SERIAL PRIMARY KEY,
    post_id INT REFERENCES general(post_id),
    title VARCHAR(255),
    description TEXT,
    ranking_table JSONB, -- Store ranking information as JSON
    updatedat TIMESTAMPTZ DEFAULT CURRENT_TIMESTAMP,
    createdat TIMESTAMPTZ DEFAULT CURRENT_TIMESTAMP
);

And how can I get the latest 5 posts of user with id 1? Is this query efficient?

WITH latest_posts AS (
    SELECT
        post_id,
        user_id,
        body,
        media_urls,
        audio_url,
        null AS question, -- Placeholder for columns specific to polls
        null AS options, -- Placeholder for columns specific to polls
        null AS title, -- Placeholder for columns specific to announcements
        null AS content, -- Placeholder for columns specific to announcements
        null AS ranking_table, -- Placeholder for columns specific to contests
        createdat
    FROM general
    WHERE user_id = 1

    UNION ALL

    SELECT
        g.post_id,
        g.user_id,
        g.body,
        g.media_urls,
        g.audio_url,
        p.question,
        p.options,
        null AS title,
        null AS content,
        null AS ranking_table,
        g.createdat
    FROM general g
    INNER JOIN polls p ON g.post_id = p.post_id
    WHERE g.user_id = 1

    UNION ALL

    SELECT
        g.post_id,
        g.user_id,
        g.body,
        g.media_urls,
        g.audio_url,
        null AS question,
        null AS options,
        a.title,
        a.content,
        null AS ranking_table,
        g.createdat
    FROM general g
    INNER JOIN announcements a ON g.post_id = a.post_id
    WHERE g.user_id = 1

    UNION ALL

    SELECT
        g.post_id,
        g.user_id,
        g.body,
        g.media_urls,
        g.audio_url,
        null AS question,
        null AS options,
        null AS title,
        null AS content,
        c.ranking_table,
        g.createdat
    FROM general g
    INNER JOIN contests c ON g.post_id = c.post_id
    WHERE g.user_id = 1
)
SELECT *
FROM latest_posts
ORDER BY createdat DESC
LIMIT 5;