返回 INNER JOIN SQL 中第二個表的第一個索引

Question

我有以下表，並想編寫一個 SQL 查詢以從與內部聯接匹配的第二個表中返回第一個結果。

Cars
id  brand       model
1   Ford        Mustang
2   Audi        A4
3   BMW         3

Images
id  img_url                                         car_id
1   https://example.s3.amazonaws.com/ford_1.jpg     1
2   https://example.s3.amazonaws.com/ford_2.jpg     1
3   https://example.s3.amazonaws.com/audi_1.jpg     2
4   https://example.s3.amazonaws.com/audi_2.jpg     2
5   https://example.s3.amazonaws.com/audi_3.jpg     2
6   https://example.s3.amazonaws.com/bmw_1.jpg      3
7   https://example.s3.amazonaws.com/bmw_2.jpg      3

我正在對cars.id = images.car_id 進行INNER JOIN，但似乎無法找到將圖像表中的結果限制為將cars.id 與images.car_id 匹配的第一行的方法。

理想情況下，我希望返回此內容：

id  brand       model       img_url
1   Ford        Mustang     https://example.s3.amazonaws.com/ford_1.jpg 
2   Audi        A4          https://example.s3.amazonaws.com/audi_1.jpg 
3   BMW         3           https://example.s3.amazonaws.com/bmw_1.jpg

非常感謝任何幫助，干杯！

Answer 1

一種方法使用row_number()

select i.*
from cars c join
     (select i.*,
             row_number() over (partition by car_id order by id) as seqnum
      from images i
     ) i
     on i.car_id = c.id
where seqnum = 1;

另一種方法將所有過濾移至where子句：

select i.*
from images i
where exists (select 1
              from cars c
              where i.car_id = c.id
             ) and
      i.id = (select min(i2.id)
              from images i2
              where i2.car_id = i.car_id
             );