Question

我是SQL查询的新手，我需要从这个查询开始进行连接：

SELECT b.Name AS VehicleName,
       a.*
FROM   VehicleDay AS a
       INNER JOIN
       Vehicles AS b
       ON a.VehicleId = b.Id
WHERE  b.SiteId = 100
       AND a.Day >= '2016-04-22'
       AND a.Day < '2016-04-28';

并在Info数据表中添加6个列：

开始（当天的第一个值）＆amp;结束（最后一天） - 累积[Cml] - 当前容量[Cap] - 总电荷[Chrg]

在Info表中，我在不同的时段获得相同VehicleId的值，我需要在日期范围内选择每天的第一个和最后一个数据。

到目前为止，我的查询看起来像这样：

SELECT b.Name AS VehicleName,
       a.*,
       c.MaxDay,
       c.Cumulative,
       c.CurrentCapacity,
       c.TotalCharge
FROM   VehicleDay AS a
       INNER JOIN
       Vehicles AS b
       ON a.VehicleId = b.Id
       INNER JOIN
       (SELECT   VehicleId,
                 MAX(TimestampLocal) AS MaxDay,
                 CAST (TimestampLocal AS DATE) AS Day,
                 Cumulative,
                 CurrentCapacity,
                 TotalCharge
        FROM     Info
        GROUP BY VehicleId, 
                 CAST (TimestampLocal AS DATE), 
                     Cumulative, CurrentCapacity, TotalCharge) AS c
       ON a.VehicleId = c.VehicleId
          AND a.Day = c.Day
WHERE  b.SiteId = 100
       AND a.Day >= '2016-04-22'
       AND a.Day < '2016-04-28';

但第二个查询返回的行数与第一个相同，我需要将行数显示为第一个。

我是否可以在不添加更多行的情况下将这6列添加到查询中？

Answer 1

重复的原因是您还要按Cumulative, CurrentCapacity, TotalCharge分组，GROUP BY可能在同一天有不同的值。那么Info每天将提供多个记录，因此将已经从其他两个表中选择的记录相乘。

您可以先获取时间戳的MIN / MAX值，然后使用这些值再次加入表SELECT b.Name AS VehicleName, a.*, c.S_Time, c.E_Time, s.Cumulative AS S_Cml, e.Cumulative AS E_Cml, s.CurrentCapacity AS S_Cap, e.CurrentCapacity AS E_Cap, s.TotalCharge AS S_Chrg, e.TotalCharge AS E_Chrg FROM VehicleDay AS a INNER JOIN Vehicles AS b ON a.VehicleId = b.Id LEFT JOIN (SELECT VehicleId, CAST (TimestampLocal AS DATE) AS Day, MIN(TimestampLocal) AS S_Time, MAX(TimestampLocal) AS E_Time FROM Info GROUP BY VehicleId, CAST (TimestampLocal AS DATE) ) AS c ON a.VehicleId = c.VehicleId AND a.Day = c.Day LEFT JOIN Info AS s ON s.VehicleId = c.VehicleId AND s.TimestampLocal = c.S_Time LEFT JOIN Info AS e ON e.VehicleId = c.VehicleId AND e.TimestampLocal = c.E_Time WHERE b.SiteId = 100 AND a.Day >= '2016-04-22' AND a.Day < '2016-04-28'两次，一次检索与MIN时间相关的列，一次用于那些与MAX时间相关：

VehicleId

有一个条件：组合TimestampLocal和#!/bin/bash rsync -av -e "ssh " $1 user@computer.domain.org:$2必须是唯一的，否则您仍会获得比预期更多的行。

SQL选择日期为最小值和最大值的位置

1 个答案: