mysql group by組內排序
有數據表 comments
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| id | newsID | comment | theTime |
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| 1 | 1 | aaa | 11 |
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| 2 | 1 | bbb | 12 |
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| 3 | 2 | ccc | 12 |
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www.2cto.com
newsID是新聞ID，每條新聞有多條評論comment，theTime是發表評論的時間
現在想要查看每條新聞的最新一條評論：
select * from comments group by newsID 顯然不行
select * from comments group by newsID order by theTime desc 是組外排序，也不行
下面有兩種方法可以實現：
www.2cto.com
（1）
selet tt.id,tt.newsID,tt.comment,tt.theTime from(
select id,newsID,comment,theTime from comments order by theTime desc) as tt group by newsID
（2）
select id,newsID,comment,theTime from comments as tt group by id,newsID,comment,theTime having
theTime=(select max(theTime) from comments where newsID=tt.newsID)
