MySQL Query: Selecting rows of linked tables and catching a "bigger" dataset
I am trying to figure out how to build a query, which satisfies the following criteria.
I have two tables. Table a
stores a list of a开发者_如何学Pythonuthors. And table b
stores a list of books. I have a linking table c
, which maps every author to one ore more books. Naturally a book can have more then one author. Given a name (let's take name = "Douglas Adams") of an author, I know that if I do
SELECT * FROM linktable
INNER JOIN a ON linktable.a_id = a.id
INNER JOIN b ON linktable.p_id = b.id
WHERE a.name = 'Douglas Adams';
I get all the books which were written by Douglas Adams. Let us assume, Douglas Adams sometimes had "coauthors". How do I get them?
I want a list the somehow looks like this:
Douglas Adams, The Hitchhiker's Guide to the Galaxy, maybe more details...
Douglas Adams, Book_2, maybe more details...
Coauthor_1, Book_2, same Details as in "Douglas Adams, Book_2, maybe more details..."
Is this doable?
I have created 3 tables, which map what I want to store and what I want to retrieve.
The 2 storage tables are:
CREATE TABLE `a` (
`id` int(11) NOT NULL AUTO_INCREMENT,
`name` varchar(100) CHARACTER SET utf8 COLLATE utf8_unicode_ci NOT NULL,
PRIMARY KEY (`id`),
UNIQUE KEY `name_UNIQUE` (`name`),
KEY `name_INDEX` (`name`),
FULLTEXT KEY `name_FULLTEXT` (`name`)
) ENGINE=MyISAM AUTO_INCREMENT=932723 DEFAULT CHARSET=utf8 COLLATE=utf8_bin
CREATE TABLE `b` (
`id` int(11) NOT NULL AUTO_INCREMENT,
`title` varchar(1000) CHARACTER SET utf8 COLLATE utf8_unicode_ci DEFAULT NULL,
PRIMARY KEY (`id`),
FULLTEXT KEY `title_fulltext` (`title`)
) ENGINE=MyISAM AUTO_INCREMENT=1617432
and one third table, which links the 2 tables above.
CREATE TABLE `linktable` (
`a_id` int(11) NOT NULL,
`b_id` int(11) NOT NULL,
KEY `a_id_INDEX` (`a_id`),
KEY `b_id_INDEX` (`b_id`)
) ENGINE=MyISAM DEFAULT CHARSET=utf8 COLLATE=utf8_unicode_ci
SELECT a2.Name, b.title
FROM a
INNER JOIN linktable lt
ON a.id = lt.a_id
INNER JOIN b
ON lt.b_id = b.id
INNER JOIN linktable lt2
ON lt.b_id = lt2.b_id
INNER JOIN a a2
ON lt2.a_id = a2.id
WHERE a.Name = 'Douglas Adams'
ORDER BY b.title,
/* Case Statement so Douglas Adams sorts before other authors */
CASE WHEN a2.Name = 'Douglas Adams' THEN 1 ELSE 2 END,
a2.Name
This should work:
SELECT * FROM b where b.id in(SELECT c.b_id
FROM a,c
WHERE a.author = "Douglas Adams"
AND a.id= c.a_id)
Edit, Alternative:
SELECT *
FROM A,B,
(SELECT c.b_id, c.a_id
FROM a,c
WHERE a.author = "Douglas Adams"
AND a.id= c.a_id) X
WHERE b.id = x.b_id
AND a.id = x.a_id
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