多个左连接的序列

Question

SELECT * FROM test_youtube Y
LEFT JOIN test_youtubelike L ON youtubelike_videoId = youtube_videoId
LEFT JOIN test_youtubeview V ON youtubeview_videoId = youtube_videoId
GROUP BY Y.id
Showing rows 0 - 29 ( 714 total, Query took 0.0062 sec)

SELECT * FROM test_youtube Y
LEFT JOIN test_youtubeview V ON youtubeview_videoId = youtube_videoId
LEFT JOIN test_youtubelike L ON youtubelike_videoId = youtube_videoId
GROUP BY Y.id
Showing rows 0 - 29 ( 714 total, Query took 0.0169 sec)

上述查询的唯一区别是左连接序列（L first，V after vs V first L later）。我认为既然两者都是独立的左连接，那么首先完成左连接就不重要了。但是，查询的速度差别很大。有什么见解吗？