Try out comments db structure with some example queries.

);

-- Example queries

-- get comments for a particular member

SELECT * FROM comments JOIN targets ON comments.target_id = targets.id

WHERE targets.sdk = ? AND targets.version = ? AND targets.type = ? AND targets.cls = ? AND targets.member = ?

AND comments.deleted = 'N'

-- get 100 most recent comments

SELECT * FROM comments JOIN targets ON comments.target_id = targets.id

WHERE targets.sdk = ? AND targets.version = ?

ORDER BY created_at DESC LIMIT 100

-- get number of comments for each target

SELECT

    target.type AS type,

    target.cls AS cls,

    target.member AS member,

    count(*) AS cnt

FROM comments JOIN targets ON comments.target_id = targets.id

WHERE target.sdk = ? AND target.version = ?

GROUP BY target.id

-- get users with the highest score

SELECT

    user.name,

    SUM(comments.rating)

FROM users JOIN comments ON comments.user_id = users.id

GROUP BY user.id