php - 多表SQL搜索查询

Question

我正在编写一个与 MySQL 数据库交互的应用程序。

我有 3 个表，“类别”、“书籍”和“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`)
);

我有 2 个变量来执行搜索。

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

我想编写以下 SQL 查询:

选择所有已读过的Python书籍(即book.read = 1)。

我的SQL知识非常有限，请帮忙。

Answer 1

这应该可以解决问题:

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'

这是一个 SQL fiddle来演示。