什麼是sql查詢刪除除最近兩個組合(channel/cdn/mediaplaylist)的2個記錄以外的所有記錄。sql:刪除每個組合(通道/ cdn/mediaplaylist)中最近2個記錄的所有記錄
例如,我有如下表:
channel cdn mediaplaylist response date
channel1 cdn1 mediaplaylist1 12 2015-02-09 10:40:00
channel2 cdn2 mediaplaylist2 19 2015-02-09 10:41:00
channel3 cdn3 mediaplaylist3 16 2015-02-09 10:42:00
channel1 cdn1 mediaplaylist1 20 2015-02-09 10:43:00
channel1 cdn1 mediaplaylist1 57 2015-02-09 10:46:00
channel2 cdn2 mediaplaylist2 83 2015-02-09 10:47:00
channel3 cdn3 mediaplaylist3 37 2015-02-09 10:48:00
channel1 cdn1 mediaplaylist1 43 2015-02-09 10:49:00
channel1 cdn1 mediaplaylist1 33 2015-02-09 10:50:00
channel2 cdn2 mediaplaylist2 79 2015-02-09 10:51:00
channel3 cdn3 mediaplaylist3 19 2015-02-09 10:52:00
channel1 cdn1 mediaplaylist1 13 2015-02-09 10:53:00
我希望得到以下結果:
channel cdn mediaplaylist response date
channel1 cdn1 mediaplaylist1 12 2015-02-09 10:40:00
channel1 cdn1 mediaplaylist1 20 2015-02-09 10:43:00
channel2 cdn2 mediaplaylist2 19 2015-02-09 10:41:00
channel2 cdn2 mediaplaylist2 83 2015-02-09 10:47:00
channel3 cdn3 mediaplaylist3 16 2015-02-09 10:42:00
channel3 cdn3 mediaplaylist3 37 2015-02-09 10:48:00
您正在使用哪些DBMS? Postgres的?甲骨文? – 2015-02-09 13:56:54
你使用的是什麼rdbms? – 2015-02-09 13:56:58
請在12篇文章後學習格式化您的問題。 – 2015-02-09 13:57:38