首頁猿問 mysql group by...

mysql group by 如何解決聊天分組取最新記錄

JavaScript

千萬里不及你 2019-04-07 11:19:22

數(shù)據(jù)結(jié)構(gòu)idsendIdreceiverIdpostDate1122015-04-0612:12:012132015-04-0612:13:013212015-04-0612:14:014232015-04-0612:15:015322015-04-0612:16:016412015-04-0612:17:017142015-04-0612:18:018242015-04-0612:19:01意思就是按照（1-2，2-1）（1-3，3-1）（1-4，4-1）（2-4,4-2)這樣分組，并且取分組最新的數(shù)據(jù)，為了實現(xiàn)聊天記錄的獲取。

查看完整描述

2 回答

梵蒂岡之花

TA貢獻1900條經(jīng)驗獲得超5個贊

假定你表名為messageselect*frommessagewhere(selectcount(*)frommessageasmwherem.sendId=message.sendIdandm.postDate>=message.postDate)<2

反對回復(fù) 2019-04-07

慕仙森

TA貢獻1827條經(jīng)驗獲得超8個贊

下面有兩種方法:假設(shè)你的表叫t_biz_sign,'最新列'字段叫create_time,需要分組的字段叫foreign_idSELECTsign.*FROMt_biz_signsignWHERENOTexists(SELECT1FROMt_biz_signWHEREforeign_id=sign.foreign_idANDsign.create_timeORDERBYcreate_timeDESC;SELECT*FROMt_biz_signsignWHERE(SELECTcount(*)FROMt_biz_signASmWHEREm.foreign_id=sign.foreign_idANDm.create_time>=sign.create_time)<2;