Question

Basicly I have a bunch of Cars that belong to dealers and the dealers have a group. The dealer table has the GROUP.ID and the Group table has the group name. A Group has multiple dealers

因此,我想估计每个群体有多少辆汽车。

我正在利用这个机会。

select  
  (select GROUP_NAME from "GROUP" where "GROUP".GROUP_ID = "DEALER"."GROUP_ID" ),
  "DEALER"."GROUP_ID" as "DEALER GROUP ID",
  "DEALER"."DEALER_NAME" as "DEALER DEALER NAME",
  "CAR"."CAR_DEALER" as "CAR DEALER"         
from 
  "CAR"
INNER JOIN 
  DEALER
ON 
  "DEALER"."DEALER_NAME" ="CAR"."CAR_DEALER"

我尝试使用<代码>group_by和count,但我看不出工作。

Answer 1

select
  g.GROUP_NAME,
  g.GROUP_ID,
  count(*) as CAR_COUNT
from
  GROUP g
  inner join DEALER d on d.GROUP_ID = g.GROUP_ID
  inner join CAR c on c.DEALER_ID = d.DEALERID
group by
  /* Also add here all field you want to select from GROUP */
  g.GROUP_NAME,
  g.GROUPID

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