如何進一步優化SQL查詢？

Question

首先，我非常喜歡SQL，現在我正在一個類項目中，其中有一些表

表用戶

user_id  |  username | name 
   1     |    nihan  |  Nihan Dip
   2     |     dip   |  Meaw ghew
  more   |  more     | more

表友

you    | friend_id  
 1     |    2
 1     |    27
 2     |    9
 more  |   more

表跟隨

user_id   |  follows
  1       |   99
  7       |   34

表帖

post_id   |  user_id  | type  |  content  | post_time
  1       |   1       |  text | loren toren | timestamp
  2       |   2       | text  | ipsum       | timestamp

現在我想由用戶朋友和他關注的人以及他的追隨者發帖，所以我做了這個SQL

SELECT 
    username, name,content, post_time
FROM
    post
        INNER JOIN
    user ON user.user_id = post.user_id
WHERE
    post.user_id IN (SELECT 
            friend_id
        FROM
            friend
        WHERE
            you = 1 

        UNION ALL 

        SELECT 
            follows
        FROM
            follow
        WHERE
            user_id = 1)
        OR post.user_id = 1
ORDER BY post_time DESC
LIMIT 10

該查詢工作正常。 我只是想知道是否可以進行優化了？ 那怎么辦 請教我 ：）

Answer 1

而不是使用IN嘗試與JOIN添加添加更多的索引 。

SELECT  DISTINCT u.name, u.username,
        p.content, p.post_time
FROM    post p
        INNER JOIN user u
            ON u.user_id = p.user_id
        INNER JOIN
        (
            SELECT  friend_id id
            FROM    friend
            WHERE   you = 1 
            UNION ALL 
            SELECT  follows id
            FROM follow
            WHERE user_id = 1
        ) s ON p.user_id = s.ID
ORDER BY post_time DESC
LIMIT 10