WordPress SQL JOIN query

If you are going to do this is SQL, use a subquery.

SELECT *,
  (SELECT meta_value 
    FROM wp_commentmeta 
    WHERE meta_key = 'your-meta-key' 
    AND wp_commentmeta.comment_id = wp_comments.comment_ID LIMIT 1) as comment_author 
FROM wp_comments

Instead of the *, enumerate the fields you want but leave out comment_author. Obviously, $wpdb functions to keep the table names straight.

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