ROW_NUMBER() 窗口函数唯一行号函数说明函数作用特点ROW_NUMBER()生成行号相同数值也分配连续唯一序号结果1,2,3,4实战案例数据表 users 用户访问表usr_idlog_date0012021/5/10022021/5/10032021/5/10012021/5/20032021/5/20012021/5/30032021/5/4建表与测试数据CREATETABLEusers(usr_idVARCHAR(10)NOTNULLCOMMENT用户ID,log_dateDATENOTNULLCOMMENT访问日期)ENGINEInnoDBDEFAULTCHARSETutf8mb4;INSERTINTOusers(usr_id,log_date)VALUES(001,2021-05-01),(002,2021-05-01),(003,2021-05-01),(001,2021-05-02),(003,2021-05-02),(001,2021-05-03),(003,2021-05-04);基于上面 users 表取出每个用户最早的 1 条访问记录。selectusr_id,log_datefrom(selectusr_id,log_date,ROW_NUMBER()over(PARTITIONbyusr_idORDERBYlog_dateasc)asrank_idfromusers)temwhererank_id1运行结果