Which of these two queries is faster/more performant?

Question

MySQL

These two queries give me what I need.

SELECT d.id, d.author_id, d.msg, d.added_time, u.name AS author_name 
FROM discussion_messages AS d, people AS u 
WHERE u.id=d.author_id AND d.discussion_id=?

SELECT d.id, d.author_id, d.msg, d.added_time, u.name AS author_name 
FROM discussion_messages d
LEFT JOIN people u ON u.id=d.author_id 
WHERE d.discussion_id=?

How to determine what will work faster? I do not like to deal with JOINs, because I did not fully understand them.

Answer 1

The queries are the same, only the syntax is different. And to compare requests, you need to look at the execution plan.
upd. Wrong. In the upper case, inner join, and in the lower case, left join (see comments by AltZ and Boris Korobkov )