PostgreSQL Question posted in
The official documentation can be found here.

Postgresql – How to apply several selects for several joins?

I want to join columns from several tables. For one table join works fine

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

But for two joins (and two selects in the first two lines I have an error)

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

Error text:

SQL Error [42601]: ERROR: syntax error at or near "select"
Position: 66

Error position: line: 2 pos: 65

How to apply two selects for two joins?

Tags:

2

Answers


  1. 0

    You do not need to use multiple selects, once you’ve join two (or more) tables, you can select anything from the resulting table, like you already did with the monitoring_stages (if I didn’t misunderstand your table schemas) :

    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;
    Login or Signup to reply.
  2. 0

    Consider:

    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 unneseccary & 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;
    Login or Signup to reply.
Please signup or login to give your own answer.

Back To Top
Search