多表SQL搜索查询

Question

I am writing an app that interacts with a MySQL database.

I have 3 tables, 'categories', 'books' and 'book_category'.

/* stores properties for categories */
`categories` (
  `id` int(11) NOT NULL auto_increment,
  `name` varchar(140) NOT NULL UNIQUE,
  PRIMARY KEY  (`id`)
);


/* stores properties for books */
`books` (
  `id` int(11) NOT NULL AUTO_INCREMENT,
  `title` int(11) NOT NULL,
  `read` tinyint(1) NOT NULL default 0, 
  `creation_date` timestamp NOT NULL default CURRENT_TIMESTAMP,
  PRIMARY KEY  (`id`)
);

/* matches books against categories */
`book_category` (
  `id` int(11) NOT NULL AUTO_INCREMENT,
  `category_id` int(11) NOT NULL,
  `item_id` int(11) NOT NULL,
  PRIMARY KEY  (`id`)
);

I have 2 variables to perform the search.

<?php
    $categoryString = 'python';  // books saved under python
    $readBool = 1;  // all books that have been read
?>

I would like to write the following SQL query:

Select all python books that have been read(i.e, book.read = 1).

My SQL knowledge is very limited, please help.

Answer 1

This should do the trick:

SELECT books.id, books.title, books.`read`, categories.name
FROM books
INNER JOIN book_category ON books.id = book_category.item_id
INNER JOIN categories ON book_category.category_id = categories.id
WHERE books.read = 1
AND categories.name = 'python'

And here's an SQL fiddle to demonstrate.