-1

我想通过删除表中的重复项来清理我的表，但保留最新版本的重复记录。

我的表格看起来类似于下面的表格。我想删除重复的航班号“AF 8253”，但保留航班号“AF 8253”，到达时间为 14:20。

id  depOrArriv flightNo airline   dest  origin  depature  arrivalTime  status
183 Arrival    AF 8253  AirUganda NULL  Nairobi NULL      14:05        Scheduled
184 Arrival    AF 8253  AirUganda NULL  Nairobi NULL      14:20        Scheduled
185 Arrival    SCAN09   SCAN Air  NULL  Kampala NULL      10:30        Scheduled

我已经尝试了下面的代码，但它似乎不起作用。

    $sql = "CREATE TEMPORARY TABLE schedule_temp AS 
              SELECT DISTINCT * FROM sortedArrivals 
              DELETE FROM sortedArrivals
              INSERT INTO sortedArrivals( 
                 timePeriod, depOrArriv, flightNo, airline, dest, 
                 origin, depature, don, arrivalTime, status) 
              SELECT timePeriod, depOrArriv, flightNo, airline, 
                 dest, origin, depature, don, arrivalTime, status 
              FROM schedule_temp";

if (!$mysqli->query($sql))
  {
    die('Error: ' . $mysqli->error);

  }

谁能帮我指出正确的方向？期待您的回音。

4

3 回答 3

1

您可以尝试这样做，假设重新安排的航班始终具有比前一个更高的RowID，并且您可以通过具有相同的flightNo、航空公司和来源来识别重复（在其他情况下，您还可以向 GROUP BY 子句添加更多变量):

DELETE FROM sortedArrivals 
WHERE RowId NOT IN 
(SELECT MAX(RowId) FROM sortedArrivals GROUP BY flightNo, airline, origin);
于 2013-10-02T17:01:08.747 回答
1

这是一个 SQL 小提琴： http ://sqlfiddle.com/#!2/a7e36/1

create table flight (id varchar(100), arrivalTime varchar(100));
insert into flight values ('8253','14:05');
insert into flight values ('8253','14:20');
insert into flight values ('8254','15:05');
insert into flight values ('8254','15:20');

DELETE FROM flight
WHERE not exists (
SELECT * FROM
(SELECT f2.ID
      , MAX(f2.arrivalTime) arrivalTime
   FROM flight f2
 GROUP BY f2.ID) x
WHERE x.ID = flight.ID and x.arrivalTime = flight.arrivalTime
);  

SELECT * from flight;

输出：

ID      ARRIVALTIME
8253    14:20
8254    15:20
于 2013-10-02T17:01:54.357 回答
0 
 DROP TABLE IF EXISTS my_table;

 CREATE TABLE my_table
 (flightNo VARCHAR(12) NOT NULL
 ,arrivalTime  TIME NOT NULL
 ,PRIMARY KEY (flightno,arrivaltime)
 );
 INSERT INTO my_table VALUES
 ('AF 8253','14:05'),        
 ('AF 8253','14:20'),
 ('SCAN09','10:30');

 SELECT * FROM my_table;
 +----------+-------------+
 | flightNo | arrivalTime |
 +----------+-------------+
 | AF 8253  | 14:05:00    |
 | AF 8253  | 14:20:00    |
 | SCAN09   | 10:30:00    |
 +----------+-------------+


  DELETE a 
    FROM my_table a
    LEFT
    JOIN 
       ( SELECT x.* 
           FROM my_table x
           JOIN 
              ( SELECT flightno
                     , MAX(arrivaltime) max_arrivaltime 
                  FROM my_table 
                 GROUP BY flightno
              ) y 
             ON y.flightno = x.flightno 
            AND y.max_arrivaltime = x.arrivaltime
       ) b
      ON b.flightno = a.flightno
     AND b.arrivaltime = a.arrivaltime
   WHERE b.flightno IS NULL;

 SELECT * FROM my_table;
 +----------+-------------+
 | flightNo | arrivalTime |
 +----------+-------------+
 | AF 8253  | 14:20:00    |
 | SCAN09   | 10:30:00    |
 +----------+-------------+
于 2013-10-02T16:59:15.083 回答