mysql - 通过多个标签选择照片

Question

我有三个 MySQL 表——照片、标签和标签照片——以及照片和标签之间的 m:n 关系。

Photos:     id | filename | ...
Tags:       id | name
Tagsphotos: photo | tag

我想选择所有符合这种条件的照片:

(tagged as "dirty" AND tagged as "road") AND (tagged as "light.front" OR tagged as "light.side") AND (tagged as "perspective.two-point")

...这意味着我想找到所有带有脏路、两点透视以及侧光或前光的图片。

我该怎么做？谢谢。

Answer 1

我认为您将不得不将标签表连接到照片表四次……非常难看。

SELECT Photos.*
FROM
  Photos
  JOIN (
    Tagsphotos JOIN Tags ON (Tags.id = Tagsphotos.tag)
  ) t1 ON (t1.photo = Photos.id)
  JOIN (
    Tagsphotos JOIN Tags ON (Tags.id = Tagsphotos.tag)
  ) t2 ON (t2.photo = Photos.id)
  JOIN (
    Tagsphotos JOIN Tags ON (Tags.id = Tagsphotos.tag)
  ) t3 ON (t3.photo = Photos.id)
  JOIN (
    Tagsphotos JOIN Tags ON (Tags.id = Tagsphotos.tag)
  ) t4 ON (t4.photo = Photos.id)
WHERE
      (t1.name = 'dirty' AND t2.name = 'road')
  AND (t3.name = 'light.front' OR t3.name = 'light.side')
  AND (t4.name = 'perspective.two-point')

子查询可能会更快:

SELECT *
FROM Photos
WHERE
  Photos.id IN (
    SELECT Tagspohotos.photo
    FROM Tagsphotos JOIN Tags ON (Tags.id = Tagsphotos.tag)
    WHERE Tags.name = 'dirty'
  )
  AND Photos.id IN (
    SELECT Tagspohotos.photo
    FROM Tagsphotos JOIN Tags ON (Tags.id = Tagsphotos.tag)
    WHERE Tags.name = 'road'
  )
  AND Photos.id IN (
    SELECT Tagspohotos.photo
    FROM Tagsphotos JOIN Tags ON (Tags.id = Tagsphotos.tag)
    WHERE Tags.name = 'light.front' OR Tags.name = 'light.side'
  )
  AND Photos.id IN (
    SELECT Tagspohotos.photo
    FROM Tagsphotos JOIN Tags ON (Tags.id = Tagsphotos.tag)
    WHERE Tags.name = 'perspective.two-point'
  )