Mysql e子查询返回的数据量。这是我的道歉！我已经编辑了我的答案。我一定会记住这一点，现在这不是什么大问题，我已经将它合并到我的PHP中，并且它已经被使用了很多次，所以我现在就不谈了。再次感谢。谢谢你的回答。比尔，我已经对你的回答竖起了大拇指，我相信这是正确的，但

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e子查询返回的数据量。这是我的道歉！我已经编辑了我的答案。我一定会记住这一点，现在这不是什么大问题，我已经将它合并到我的PHP中，并且它已经被使用了很多次，所以我现在就不谈了。再次感谢。谢谢你的回答。比尔，我已经对你的回答竖起了大拇指，我相信这是正确的，但如果我说实话，我不懂语法。@JackTrowbridge，从阅读本页开始：

id   | ads_post_id
---------------------------------------------------------------------------
22   | 983314845117571
23   | 983314845117571
24   | 983314845117571         
104  | 983314845117571
250  | 983314845117571
253  | 983314845117571 
767  | 983314845117571          
---------------------------------------------------------------------------

SELECT * FROM fb_ads GROUP BY ads_post_id ORDER BY id DESC LIMIT 6

id   | ads_post_id
---------------------------------------------------------------------------
22   | 983314845117571   
---------------------------------------------------------------------------

id    | ads_post_id
---------------------------------------------------------------------------
767   | 983314845117571   
---------------------------------------------------------------------------

SELECT * FROM 
(
select * from fb_ads order by id desc
) as fb_ads
group by ads_post_id
order by id DESC LIMIT 6

   ---------------------------------------------------------------------------
    id   | ads_post_id
    ---------------------------------------------------------------------------
    22   | 983314845117571   
    ---------------------------------------------------------------------------

SELECT max(id), ads_post_id FROM fb_ads GROUP BY ads_post_id LIMIT 6

SELECT id, ads_post_id
FROM (
    SELECT id, ads_post_id,
      @r := IF(@g=ads_post_id, @r+1, 1) AS row_number,
      @g := ads_post_id
    FROM (SELECT @r:=1, @g:=0) as _init, fb_ads
    ORDER BY ads_post_id, id DESC
) AS t
WHERE t.row_number <= 6;

SELECT ads_post_id, MAX(id) 
FROM fb_ads 
GROUP BY ads_post_id 
LIMIT 6

id   | ads_post_id         ip_address
---------------------------------------------------------------------------
22   | 983314845117571     192.168.0.0
23   | 983314845117571     192.168.0.5
24   | 983314845117571     192.168.0.7    
104  | 983314845117571     192.168.0.0
250  | 983314845117571     192.168.0.4
253  | 983314845117571     192.168.0.6
767  | 983314845117571     192.168.0.1     
---------------------------------------------------------------------------

SELECT ads_post_id, MAX(id), MAX(ip_address) 
FROM fb_ads 
GROUP BY ads_post_id 
LIMIT 6

id   | ads_post_id         ip_address
---------------------------------------------------------------------------
767  | 983314845117571     192.168.0.7     
---------------------------------------------------------------------------

SELECT ads_post_id, MAX(id), ip_address 
FROM fb_ads 
GROUP BY ads_post_id 
LIMIT 6

SELECT a.ads_post_id,
        a.id,
        a.ip_address
FROM fb_ads a
INNER JOIN
(
    SELECT ads_post_id, MAX(id) AS max_id 
    FROM fb_ads 
    GROUP BY ads_post_id 
) sub0
ON a.ads_post_id = sub0.ads_post_id
AND a.id = sub0.max_id

SELECT a.ads_post_id,
        SUBSTRING_INDEX(GROUP_CONCAT(id ORDER BY id DESC), ',', 1),
        SUBSTRING_INDEX(GROUP_CONCAT(ip_address ORDER BY id DESC), ',', 1)
FROM fb_ads 
GROUP BY ads_post_id 

SELECT   *
FROM     fb_ads
WHERE    (id, ads_post_id) IN (
           SELECT   MAX(id), ads_post_id
           FROM     fb_ads
           GROUP BY ads_post_id)
ORDER BY id DESC LIMIT 6