对于大型数据库，MySQL Left Join 1结果

Question

I have a big database of movies and I want to search movies by years and genres.

I have 3 table to deal with:

1. movies (Key TITLE_ID)
2. movie2genre (TITLE_ID + GENRE_ID)
3. genre (Key GENRE_ID)

movies:

+----------+---------------+------+
| TITLE_ID |     TITLE     | YEAR |
+----------+---------------+------+
|  10001   | Matrix        | 1999 |
|  10002   | Walk on Water | 2004 |
+----------+---------------+------+

movie2genre:

+----------+----------+
| TITLE_ID | GENRE_ID |
+----------+----------+
|  10001   |    1     |
|  10001   |    2     |
|  10002   |    2     |
|  10002   |    4     |
|  10001   |    3     |
+----------+----------+

genre:

+----------+-----------+
| GENRE_ID | GENRE_TXT |
+----------+-----------+
|    1     | Action    |
|    2     | Adventure |
|    3     | Thriller  |
|    4     | Fantasy   |
+----------+-----------+

A user sends a request for year 1999, genre Adventure or Thriller.

How can I find all movies in 1 optimized query?

Result should be:

+----------+--------+------+-----------+
| TITLE_ID | TITLE  | YEAR | GENRE_TXT |
+----------+--------+------+-----------+
|  10001   | Matrix | 1999 |  Action   |
+----------+--------+------+-----------+

I don't care which genre gets selected, only that this movie as 1 of genres user ask for.

Answer 1

You can try joining together the 3 tables and then restricting the query with a WHERE clause using your requirements for year and movie genre. The query below will return only one record, which you specified would be acceptable.

SELECT m.TITLE_ID, m.TITLE, m.YEAR, g.GENRE_TXT
FROM movies m
INNER JOIN movie2genre mg ON m.TITLE_ID = mg.TITLE_ID
INNER JOIN genre g ON mg.GENRE_ID = g.GENRE_ID
WHERE m.YEAR = 1999 AND g.GENRE_TXT IN ('Adventure', 'Thriller')