如何获取与帖子ID匹配的标签并显示记录

Question

伙计们，我有以下表格

1. 帖子
2. 标签
3. post_tags

我将post_tags表中的postID和tagsID保存为post_id，tag_id

现在我希望在我的 post.php 页面中显示与标签匹配的帖子，但是如何进行查询以获取匹配的标签？

$stmt = $db->query('SELECT * FROM posts WHERE postID LIKE "%'.$id.'%"');                
                $stmt->execute();
                while($rw = $stmt->fetch()){

}

我在这里分享我的实际数据结构以及数据是如何保存到每个表中的，希望这能给你一个想法来帮助我处理 JOIN 表？

这是 3 张桌子

--
-- Table structure for table `blog_posts`
--

CREATE TABLE IF NOT EXISTS `blog_posts` (
  `postID` int(11) unsigned NOT NULL AUTO_INCREMENT,
  `posterID` int(11) NOT NULL,
  `catID` int(11) NOT NULL,
  `postTitle` varchar(90) DEFAULT NULL,
  `postImg` varchar(255) DEFAULT NULL,
  `postYoutube` varchar(100) DEFAULT NULL,
  `postSlug` varchar(255) DEFAULT NULL,
  `postDesc` text,
  `postCont` text,
  `postViews` int(11) NOT NULL DEFAULT '0',
  `postDate` datetime DEFAULT NULL,
  PRIMARY KEY (`postID`)
) ENGINE=InnoDB  DEFAULT CHARSET=latin1 AUTO_INCREMENT=4 ;

--
-- Dumping data for table `blog_posts`
--

INSERT INTO `blog_posts` (`postID`, `posterID`, `catID`, `postTitle`, `postImg`, `postYoutube`, `postSlug`, `postDesc`, `postCont`, `postViews`, `postDate`) VALUES
(1, 1, 1, ' Lorem Ipsum, giving information on its origins, as well as a random Lipsum generator.', ' Lorem Ipsum, giving information on its origins, as well as a random Lipsum generator.jpg', '', '1/lorem-ipsum-giving', '<p> Lorem Ipsum, giving information on its origins, as well as a random Lipsum generator.</p>', '<p> Lorem Ipsum, giving information on its origins, as well as a random Lipsum generator.</p>', 1, '2017-08-10 11:46:36'),
(2, 1, 3, ' Lorem Ipsum, giving information on its origins, as well as a random Lipsum generator.', ' Lorem Ipsum, giving information on its origins, as well as a random Lipsum generator.jpg', '', '2/lorem-ipsum-giving', '<p>Lorem Ipsum, giving information on its origins, as well as a random Lipsum generator.</p>', '<p>Lorem Ipsum, giving information on its origins, as well as a random Lipsum generator.</p>', 0, '2017-08-10 13:38:57'),
(3, 1, 2, 'Lorem Ipsum, giving information on its origins, as well as a random Lipsum generator.', 'Lorem Ipsum, giving information on its origins, as well as a random Lipsum generator.jpg', '', '3/moong-dal-halwa', '<p>Lorem Ipsum, giving information on its origins, as well as a random Lipsum generator.</p>', '<p>Lorem Ipsum, giving information on its origins, as well as a random Lipsum generator.</p>', 0, '2017-08-10 13:39:40'));

-- --------------------------------------------------------

--
-- Table structure for table `blog_posts_tags`
--

CREATE TABLE IF NOT EXISTS `blog_posts_tags` (
  `id` int(11) NOT NULL AUTO_INCREMENT,
  `post_id` int(11) NOT NULL,
  `tag_id` int(11) NOT NULL,
  PRIMARY KEY (`id`),
  UNIQUE KEY `blog_posts_tags` (`post_id`,`tag_id`)
) ENGINE=InnoDB  DEFAULT CHARSET=latin1 AUTO_INCREMENT=31 ;

--
-- Dumping data for table `blog_posts_tags`
--

INSERT INTO `blog_posts_tags` (`id`, `post_id`, `tag_id`) VALUES
(1, 1, 2),
(7, 1, 4),
(9, 1, 3),
(2, 1, 3),
(10, 1, 2),
(8, 1, 5),
(4, 1, 5),
(24, 2, 2),
(25, 3, 5),
(26, 3, 1));

-- --------------------------------------------------------

--
-- Table structure for table `blog_tags`
--

CREATE TABLE IF NOT EXISTS `blog_tags` (
  `tagID` int(11) NOT NULL AUTO_INCREMENT,
  `tagName` varchar(32) NOT NULL,
  `tagUrl` varchar(32) NOT NULL,
  PRIMARY KEY (`tagID`)
) ENGINE=InnoDB  DEFAULT CHARSET=latin1 AUTO_INCREMENT=61 ;

--
-- Dumping data for table `blog_tags`
--

INSERT INTO `blog_tags` (`tagID`, `tagName`, `tagUrl`) VALUES
(1, 'American Food', 'american-food'),
(2, 'Bakeries', 'bakeries'),
(3, 'Bars', 'bars'),
(4, 'Beef', 'beef'),
(5, 'Cafe', 'cafe');

有什么帮助吗？

Answer 1

你需要使用JOIN，例如：

SELECT *
FROM blog_posts bp JOIN blog_posts_tags bpt ON bp.postID = bpt.post_id
JOIN blog_tags bt ON bt.tagID = bpt.tag_id
WHERE bt.tagName = 'Bakeries';

如果要通过id搜索，可以在WHERE条件下使用t.id，例如：

SELECT *
FROM blog_posts bp JOIN blog_posts_tags bpt ON bp.postID = bpt.post_id
JOIN blog_tags bt ON bt.tagID = bpt.tag_id
WHERE bt.tagID = 2;

这里，id对应于post和tag的id（在各自的表中），post_id和tag_id是post_tags表中对应外键列的名称。

这是SQL Fiddle。