Can I do an SQL query on a table and its join table at the same time?

I have a couple tables that look like this:

 ___________    ___________
| Books     |  | Tags      开发者_如何学Go|
|-----------|  |-----------|
| book_id   |  | tag_id    |
| book_name |  | tag_name  |
 -----------    ----------- 

And a join table that connects the "many-to-many relationship":

 ___________
| Books/Tags|
|-----------|
| book_id   |
| tag_id    |
 -----------

I have the following query:

SELECT book_name, tag_name FROM books 
JOIN books_tags ON books.book_id = books_tags.book_id 
JOIN tags ON tags.tag_id = books_tags.tag_id 
WHERE books.book_id = 283

And the following (for books that aren't tagged):

SELECT book_name FROM books WHERE books.book_id = 283

Is there a way to merge those two queries into one?

---

You want a LEFT join

SELECT book_name, 
       tag_name 
FROM   books 
       LEFT JOIN books_tags 
         ON books.book_id = books_tags.book_id 
       LEFT JOIN tags 
         ON tags.tag_id = books_tags.tag_id 
WHERE  books.book_id = 283 

---

Do your first query but use a LEFT JOIN for the first join clause. A left join in this case gives you all records from the books table, regardless of matches, along with matching rows that are joined.

---

you could (thanks for the comment!) use union . I am not sure what you mean with " merge those two queries into one "

SELECT book_name, tag_name FROM books JOIN books_tags ON books.book_id = books_tags.book_id JOIN tags ON tags.tag_id = books_tags.tag_id WHERE books.book_id = 283

UNION

SELECT book_name,'' FROM books WHERE books.book_id = 283

---

You can use LEFT JOIN instead of jOIN to merge both queries.

Take a look at this documentation.