为什么在 WHERE 子句中使用硬编码值时在 Group BY 语句中出现错误？答案

【问题标题】：Why am I getting Error in Group BY statement while using hardcoded values in WHERE clause?为什么在 WHERE 子句中使用硬编码值时在 Group BY 语句中出现错误？
【发布时间】：2018-11-06 09:28:22
【问题描述】：

我是 PostgreSQL 新手。我正在开发出租车预订应用程序。

我试图找出 (1) 不起作用的原因。硬编码值将被用户输入替换。

不工作：

选择 MAX(cr.pickup_point) AS Pickup_point ， MAX(cr.destination) AS 目的地， MAX(cr.leave_time) AS leave_time,MAX(cr.license) AS license , MAX(cr.username) AS 用户名，MAX(cr.car_ride_id) AS car_ride_id ， MAX(isd.no_of_seats) AS no_of_seats FROM car_ride cr , is_driver isd WHERE cr.username = isd.username 和 cr.license = isd.license 和 LOWER(TRIM(pickup_point))::varchar = LOWER(TRIM('Paya Lebar East, Paya Lebar'))::varchar AND (LOWER(TRIM(cr.destination))::varchar = LOWER(TRIM('Kranji, Sungei Kadut'))::varchar AND (cr.leave_time)> now()::timestamp(0) 分组（cr.car_ride_id，isd.no_of_seats） HAVING isd.no_of_seats> ALL (SELECT COUNT(*) FROM bids b , car_ride cr2 WHERE b.driver_username = cr2.username AND b.successful 为真 AND b.leave_time >now()::timestamp(0) AND cr2.leave_time = b.leave_time 和 cr.car_ride_id = cr2.car_ride_id)

2.工作：

SELECT  MAX(cr.pickup_point) AS pickup_point , MAX(cr.destination)
AS destination , MAX(cr.leave_time) AS leave_time ,
MAX(cr.license) AS license , MAX(cr.username)
AS username, MAX(cr.car_ride_id) AS car_ride_id , MAX(isd.no_of_seats) AS no_of_seats
FROM car_ride  cr , is_driver isd WHERE cr.username = isd.username
AND cr.license =  isd.license AND
(cr.leave_time)> now()::timestamp(0) GROUP BY(cr.car_ride_id, isd.no_of_seats)  HAVING
isd.no_of_seats>
ALL (SELECT COUNT(*) FROM bids b , car_ride cr2 WHERE
b.driver_username = cr2.username AND b.successful IS TRUE
AND  b.leave_time >now()::timestamp(0) AND cr2.leave_time = b.leave_time
AND cr.car_ride_id = cr2.car_ride_id )

(1.) 和 (2.) 的区别在于前者打算根据接送点和目的地过滤结果。

虽然 (2) 显示所有未来且未完全预订的乘车广告（特定 car_ride_id >

请注意，我已多次使用 MAX 聚合，因为我已将它们用作后续表单中的隐藏字段以进行投标。

Results for 2nd query

Error message upon running the 1st query.

错误：“GROUP”或附近的语法错误

第 10 行：分组依据（cr.car_ride_id, isd.no_of_seats）

【问题讨论】：

@B001 已编辑。感谢您的建议

标签： php database postgresql group-by phppgadmin

【解决方案1】：

在AND 和LOWER 之间有一个没有关闭的不必要括号：

  AND (LOWER(TRIM(cr.destination))::varchar = LOWER(TRIM('Kranji, Sungei Kadut'))::varchar

固定：

SELECT MAX(cr.pickup_point) AS pickup_point , MAX(cr.destination) AS destination,
       MAX(cr.leave_time) AS leave_time,MAX(cr.license) AS license ,
       MAX(cr.username) AS username, MAX(cr.car_ride_id) AS car_ride_id ,
       MAX(isd.no_of_seats) AS no_of_seats
  FROM car_ride cr , is_driver isd
 WHERE cr.username = isd.username
   AND cr.license = isd.license
   AND LOWER(TRIM(pickup_point))::varchar = LOWER(TRIM('Paya Lebar East, Paya Lebar'))::varchar
   AND /*(*/LOWER(TRIM(cr.destination))::varchar = LOWER(TRIM('Kranji, Sungei Kadut'))::varchar
   AND (cr.leave_time)> now()::timestamp(0)
 GROUP BY(cr.car_ride_id, isd.no_of_seats)
HAVING isd.no_of_seats> ALL (SELECT COUNT(*)
                               FROM bids b , car_ride cr2
                              WHERE b.driver_username = cr2.username
                                AND b.successful IS TRUE
                                AND b.leave_time >now()::timestamp(0)
                                AND cr2.leave_time = b.leave_time
                                AND cr.car_ride_id = cr2.car_ride_id)

当您以更易读的方式格式化查询时，更容易避免这些错误。

【讨论】：