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Accepted
mascai
Asked: 2024-09-24 17:54:50 +0800 CST

如何对多个连接应用多个选择？

  • 772

我想连接多个表中的列。对于一个表，连接工作正常

select org.catalog_truck.plate_number as "Госномер грузовика",
shift_id as "ID смены",
trip_id as "ID рейса",
*
from core.monitoring_stages
join org.catalog_truck
on vehicle_id = org.catalog_truck.catalog_truck_id
where gen_id = (SELECT max(gen_id)
FROM core.monitoring_tripmachine_generation
WHERE ready=true and timerange_from > '2024-09-23 00:00:00.000 +0300' and timerange_to < '2024-09-23 23:59:59.000 +0300')
ORDER by dtstart

但是对于两个连接（以及前两行中的两个选择，我有一个错误）

select org.catalog_truck.plate_number as "Госномер грузовика",
select org.catalog_field.name as "Поле погрузки",   <--- select for the second join (error in this line)
shift_id as "ID смены",
trip_id as "ID рейса",
*
from core.monitoring_stages
join org.catalog_truck
on vehicle_id = org.catalog_truck.catalog_truck_id
where gen_id = (SELECT max(gen_id)
from core.monitoring_stages <--- second join
join org.catalog_field cf 
on field_id = org.catalog_field.name
FROM core.monitoring_tripmachine_generation
WHERE ready=true and timerange_from > '2024-09-23 00:00:00.000 +0300' and timerange_to < '2024-09-23 23:59:59.000 +0300')
ORDER by dtstart

错误文本：

SQL 错误 [42601]：错误：“select”处或附近的语法错误 位置：66

错误位置：行：2 位置：65

如何对两个连接应用两个选择？

sql

2 个回答

  1. 考虑：

    SELECT ct.plate_number AS "Госномер грузовика"
     , cf.name AS "Поле погрузки"
     , ms.shift_id AS "ID смены"
     , ms.trip_id AS "ID рейса"
     , *  --  typically unnecessary & inefficient to include all columns in the result!
FROM   core.monitoring_stages ms
LEFT   JOIN org.catalog_truck ct ON ct.catalog_truck_id = ms.vehicle_id  -- LEFT JOIN = safe way
LEFT   JOIN org.catalog_field cf ON cf.catalog_field_id = ms.field_id
WHERE  ms.gen_id = (
   SELECT max(gen_id)
   FROM   core.monitoring_tripmachine_generation
   WHERE  ready                                   -- boolean can be used directly
   AND    timerange_from >= '2024-09-23 0:0 +03'  -- the day 2024-09-23 filtered properly
   AND    timerange_to   <  '2024-09-24 0:0 +03'
   )
ORDER  BY ms.dtstart;
    • 2
  2. Best Answer

    您不需要使用多个选择，一旦您连接了两个（或更多）表，您就可以从结果表中选择任何内容，就像您已经对monitoring_stages所做的那样（如果我没有误解您的表模式的话）：

    select 
    org.catalog_truck.plate_number as "Госномер грузовика",
    org.catalog_field.name as "Поле погрузки",   -- Second join column
    shift_id as "ID смены",
    trip_id as "ID рейса",
    *
from 
    core.monitoring_stages
join 
    org.catalog_truck 
    on vehicle_id = org.catalog_truck.catalog_truck_id
join 
    org.catalog_field  -- Second table join
    on field_id = org.catalog_field.catalog_field_id
where 
    gen_id = (SELECT max(gen_id)
              FROM core.monitoring_tripmachine_generation
              WHERE ready = true 
              and timerange_from > '2024-09-23 00:00:00.000 +0300' 
              and timerange_to < '2024-09-23 23:59:59.000 +0300')
ORDER by dtstart;
    • 0

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