Relating categories with tags using SQL
I want be able to find tags of items under the a certain category. Following is example of my database design:
images
+----------+-----+-------------+-----+
| image_id | ... | category_id | ... |
+----------+-----+-------------+-----+
| 1 | ... | 11 | ... |
+----------+-----+---开发者_如何学JAVA----------+-----+
| 2 | ... | 12 | ... |
+----------+-----+-------------+-----+
| 3 | ... | 11 | ... |
+----------+-----+-------------+-----+
| 4 | ... | 11 | ... |
+----------+-----+-------------+-----+
images_tags
+----------+--------+
| image_id | tag_id |
+----------+--------+
| 1 | 53 |
+----------+--------+
| 3 | 54 |
+----------+--------+
| 2 | 55 |
+----------+--------+
| 1 | 56 |
+----------+--------+
| 4 | 57 |
+----------+--------+
tags and categories each have their own table relating the id to an actual name(text).
So my question is how will i find out that images with category_id
=11 have have the tag_id
53 54 56 57.
In other words how to find the tags that images in certain category have?
Maybe an inner SELECT would do it? Something like:
SELECT tag_id FROM images_tags WHERE image_id IN (SELECT image_id FROM images WHERE cateory_id = 11 )
try this:
SELECT images.*, tags.* from images, tags where images.image_id = images_tags.image_id and images.category_id = X;
Where X is the desired category.
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