Question

Ok, I’ve run into the situation. 3 tables, tags, books, and the intersection table*. How do you deal with this again?

tags
  -id    int
  -name  varchar

books
  -id    int
  -name  varchar

taggings
  -tagId_fk   int
  -bookId_fk  int

Sample data

tags
  id   name
   1   good
   2   really good
   3   bad
   4   long
   5   exciting

books
  id      name
   1      Pumpkin Man
   2      O-castic Bastard

taggings
  bookId_fk     tagId_fk
  1             1
  1             4
  2             4
  2             5

So here Pumpkin Man has been tagged as good and long while O-castic Bastard has been tagged as long and exciting.

I want to write a single query that retrieves:

books.id   books.name      taggings.tagId_fk as tags.name (know what I mean?)
1          Pumpkin Man        good
1          Pumpkin Man        long
2          O-castic Bastard   long
2          O-castic Bastard   exciting

Not exactly what I want

SELECT DISTINCT taggings.bookId_fk, tags.name FROM tags
  INNER JOIN taggings ON taggings.tagId_fk=tags.tagId
  ORDER BY taggings.bookId_fk;

The question I really have is, is it even possible to display the above result in MySQL without:

• Breaking it into more than one query,
• Using a subquery at all?

*PS I know that some people don’t use an intersection table

Answer 1

    SELECT b.*,
           t.name
      FROM books b
INNER JOIN taggings t_b ON t_b.bookId_fk = b.id
INNER JOIN tags t ON t.id = t_b.tagId_fk
  ORDER BY b.id

So, yes, it is possible.

Note: if you have the books without tags at all – change INNER to LEFT in both cases and you’ll get the NULL value instead of tag for that books.