SQL：选择列值与上一行不同的行

SELECt a.*FROM tableX AS aWHERe a.StatusA <>      ( SELECt b.StatusA        FROM tableX AS b        WHERe a.System = b.System          AND a.Timestamp > b.Timestamp        ORDER BY b.Timestamp DESC        LIMIT 1      )

但是您也可以尝试使用此方法（在上使用索引

(System,Timestamp)

SELECt System, Timestamp, StatusA, StatusBFROM  ( SELECt (@statusPre <> statusA AND @systemPre=System) AS statusChanged         , System, Timestamp, StatusA, StatusB         , @statusPre := StatusA         , @systemPre := System    FROM tableX       , (SELECT @statusPre:=NULL, @systemPre:=NULL) AS d    ORDER BY System, Timestamp  ) AS goodWHERe statusChanged ;