Question

没有实际提供我的查询的所有细节：有没有办法在不同的表上加入两个单独查询的结果？例如，如果我有一张桌子

result_table1

id name address
1  Joe  5 Street
2  Max  6 road
3  Jon  4 place

result_table2

id  occupation 
1    Student
2    Lawer
3    Carpenter

新表

id name address   occupation
1  Joe  5 Street  Student
2  Max  6 road    Lawer
3  Jon  4 place   Carpenter

如果前两个表只是表，我会使用左连接，但前两个表实际上是由其他使用计数和总和的select语句组成的。当我尝试组合两个select语句时，分组会给我带来意想不到的结果。

真实世界示例

据我所知，当我没有提出一个实际的例子时，这一点很难解决。

第一个查询

SELECT 

bbs.id AS bb_id,
count(bb_replies.bbs_id) AS num_replies,
bb_locations.title AS location,
bb_locations.description AS location_description,
bb_categories.title AS category,
bb_categories.description AS category_description,
users.first_name AS first_name,
users.last_name as last_name,
users.id AS user_id,
bbs.title AS post_title,
bbs.content,
bbs.created_date,
bbs.rank 

FROM `bbs` 

LEFT JOIN bb_locations ON bbs.bb_locations_id = bb_locations.id 
LEFT JOIN bb_categories ON bbs.bb_categories_id = bb_categories.id 
LEFT JOIN users ON bbs.users_id = users.id 
LEFT JOIN bb_replies ON bbs.id = bb_replies.bbs_id 

GROUP BY bb_id,location,location_description,category,category_description,first_name,last_name,user_id,post_title,content,created_date,rank

第二个查询

SELECT bbs_id,
       sum(CASE WHEN user_id = 2 THEN like_dislike END) AS thisUsersRating,
       SUM(CASE WHEN like_dislike = 1 THEN 1 ELSE 0 END) AS likes, 
       SUM(CASE WHEN like_dislike = 0 THEN 1 ELSE 0 END) AS dislikes
FROM bb_ratings
GROUP BY bbs_id

如何以分组不会产生奇怪结果的方式加入这两个查询？

数据库

-- phpMyAdmin SQL Dump
-- version 3.2.4
-- http://www.phpmyadmin.net
--
-- Host: localhost
-- Generation Time: Nov 26, 2010 at 05:28 PM
-- Server version: 5.1.41
-- PHP Version: 5.3.1

SET SQL_MODE="NO_AUTO_VALUE_ON_ZERO";

--
-- Database: `bulletin_board_application`
--

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

--
-- Table structure for table `bbs`
--

CREATE TABLE IF NOT EXISTS `bbs` (
  `id` int(11) NOT NULL AUTO_INCREMENT,
  `bb_locations_id` int(11) NOT NULL,
  `bb_categories_id` int(11) NOT NULL,
  `users_id` int(11) NOT NULL,
  `title` varchar(255) NOT NULL,
  `content` text NOT NULL,
  `created_date` int(11) NOT NULL,
  `rank` int(11) NOT NULL,
  PRIMARY KEY (`id`)
) ENGINE=MyISAM  DEFAULT CHARSET=latin1 AUTO_INCREMENT=5 ;

--
-- Dumping data for table `bbs`
--

INSERT INTO `bbs` (`id`, `bb_locations_id`, `bb_categories_id`, `users_id`, `title`, `content`, `created_date`, `rank`) VALUES
(1, 1, 2, 1, 'Bulletin post 2', 'This is the content of my second bulletin post', 1290792252, 2),
(2, 1, 2, 1, 'Bulletin post 1', 'The content of my first bulletin post', 1290792124, 1),
(3, 1, 2, 2, 'Bulletin Post 3', 'This is the content of bulletin post 3\r\n', 1290792555, 3),
(4, 2, 1, 1, 'bulletin post 4', 'This is my fourth bulletin post', 1290800287, 4);

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

--
-- Table structure for table `bb_categories`
--

CREATE TABLE IF NOT EXISTS `bb_categories` (
  `id` int(11) NOT NULL AUTO_INCREMENT,
  `title` varchar(255) NOT NULL,
  `description` varchar(255) NOT NULL,
  `order` varchar(255) NOT NULL,
  `admin` int(11) NOT NULL,
  PRIMARY KEY (`id`)
) ENGINE=MyISAM  DEFAULT CHARSET=latin1 AUTO_INCREMENT=3 ;

--
-- Dumping data for table `bb_categories`
--

INSERT INTO `bb_categories` (`id`, `title`, `description`, `order`, `admin`) VALUES
(1, 'Free Stuff', 'Free stuff in the office', '1', 2),
(2, 'Office Anouncements', 'This is an anouncement for the office', '2', 3);

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

--
-- Table structure for table `bb_locations`
--

CREATE TABLE IF NOT EXISTS `bb_locations` (
  `id` int(11) NOT NULL AUTO_INCREMENT,
  `title` varchar(255) NOT NULL,
  `description` varchar(255) NOT NULL,
  `address` varchar(255) NOT NULL,
  `order` int(11) NOT NULL,
  PRIMARY KEY (`id`)
) ENGINE=MyISAM  DEFAULT CHARSET=latin1 AUTO_INCREMENT=3 ;

--
-- Dumping data for table `bb_locations`
--

INSERT INTO `bb_locations` (`id`, `title`, `description`, `address`, `order`) VALUES
(1, 'Washington DC', 'Washington DC chinatown office', 'H street chinatown 20001', 0),
(2, 'San Francisco', 'San Francisco office', 'g street in sf 20395', 1);

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

--
-- Table structure for table `bb_ratings`
--

CREATE TABLE IF NOT EXISTS `bb_ratings` (
  `id` int(11) NOT NULL AUTO_INCREMENT,
  `bbs_id` int(11) NOT NULL,
  `user_id` int(11) NOT NULL,
  `like_dislike` int(11) NOT NULL,
  PRIMARY KEY (`id`)
) ENGINE=MyISAM  DEFAULT CHARSET=latin1 AUTO_INCREMENT=16 ;

--
-- Dumping data for table `bb_ratings`
--

INSERT INTO `bb_ratings` (`id`, `bbs_id`, `user_id`, `like_dislike`) VALUES
(15, 4, 2, 0),
(14, 4, 1, 0),
(13, 3, 1, 0),
(12, 2, 1, 1),
(11, 1, 2, 0),
(10, 1, 1, 1);

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

--
-- Table structure for table `bb_replies`
--

CREATE TABLE IF NOT EXISTS `bb_replies` (
  `id` int(11) NOT NULL AUTO_INCREMENT,
  `users_id` int(11) NOT NULL,
  `bbs_id` int(11) NOT NULL,
  `content` text NOT NULL,
  `created_date` int(11) NOT NULL,
  `rank` int(11) NOT NULL,
  PRIMARY KEY (`id`)
) ENGINE=MyISAM  DEFAULT CHARSET=latin1 AUTO_INCREMENT=10 ;

--
-- Dumping data for table `bb_replies`
--

INSERT INTO `bb_replies` (`id`, `users_id`, `bbs_id`, `content`, `created_date`, `rank`) VALUES
(1, 1, 1, 'This is a response to the bulletin post with an id of 1', 1290799543, 1),
(2, 1, 1, 'This is a second response to the post with an id of 1', 1290799778, 1),
(3, 1, 2, 'This is a response to the bulletin post with an id of 2\r\n', 1290799827, 1),
(4, 1, 2, 'This is a second response to the bulletin post with an id of 2\r\n', 1290799858, 1),
(5, 1, 3, 'Reply to bulletin with an id of 3', 1290799924, 1),
(6, 1, 3, 'Another reply to the post which has an id of 3\r\n', 1290799962, 1),
(7, 1, 1, 'This is a third reply for the bulletin post with an id of 1\r\n', 1290801268, 1),
(8, 1, 2, '3rd reply for bulletin with id = 2', 1290801445, 2),
(9, 1, 2, '3rd reply for bulletin with id = 2', 1290808030, 3);

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

--
-- Table structure for table `bb_reply_ratings`
--

CREATE TABLE IF NOT EXISTS `bb_reply_ratings` (
  `id` int(11) NOT NULL AUTO_INCREMENT,
  `bb_replies_id` int(11) NOT NULL,
  `user_id` int(11) NOT NULL,
  `like_dislike` tinyint(11) NOT NULL,
  PRIMARY KEY (`id`)
) ENGINE=MyISAM  DEFAULT CHARSET=latin1 AUTO_INCREMENT=11 ;

--
-- Dumping data for table `bb_reply_ratings`
--


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

--
-- Table structure for table `bb_sort_bys`
--

CREATE TABLE IF NOT EXISTS `bb_sort_bys` (
  `id` int(11) NOT NULL AUTO_INCREMENT,
  `title` varchar(20) NOT NULL,
  `description` varchar(255) NOT NULL,
  PRIMARY KEY (`id`)
) ENGINE=MyISAM  DEFAULT CHARSET=latin1 AUTO_INCREMENT=3 ;

--
-- Dumping data for table `bb_sort_bys`
--

INSERT INTO `bb_sort_bys` (`id`, `title`, `description`) VALUES
(1, 'Newest', 'Posts are sorted by their creation date'),
(2, 'Popular', 'Posts are sorted by their rank');

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

--
-- Table structure for table `users`
--

CREATE TABLE IF NOT EXISTS `users` (
  `id` int(11) NOT NULL AUTO_INCREMENT,
  `user_name` varchar(10) NOT NULL,
  `first_name` varchar(100) NOT NULL,
  `last_name` varchar(100) NOT NULL,
  `permission` int(1) NOT NULL,
  `bb_sort_bys_id` varchar(10) NOT NULL,
  `bb_locations_csv` varchar(255) NOT NULL,
  `bb_categories_csv` varchar(255) NOT NULL,
  `total_bulletins` int(5) NOT NULL,
  `bulletins_per_page` int(5) NOT NULL,
  PRIMARY KEY (`id`)
) ENGINE=MyISAM  DEFAULT CHARSET=latin1 AUTO_INCREMENT=4 ;

--
-- Dumping data for table `users`
--

INSERT INTO `users` (`id`, `user_name`, `first_name`, `last_name`, `permission`, `bb_sort_bys_id`, `bb_locations_csv`, `bb_categories_csv`, `total_bulletins`, `bulletins_per_page`) VALUES
(1, 'ahughesg', 'Andrew', 'Hughes-Games', 1, '1', '1,2', '1,2', 20, 5),
(2, 'joeblack', 'Joe', 'Black', 3, '2', '1,2', '1,2', 20, 2),
(3, 'jondoe', 'Jon', 'Doe', 3, '1', '1,2', '1,2', 20, 4);

Answer 1

使用前两个表的临时表，然后使用它们来进行连接，但我想你可能有问题，因为没有共同的属性可以加入，除非你希望使用表的id，如果它们碰巧匹配< / p>

Answer 2

完成@Microgen的答案......既然你已经有两个第一个选择工作，你可以将这些结果保存在临时表中：

create temporary table tmp1 as <your first select>;
alter table tmp1 add <some index to accelerate your join later>;
create temporary table tmp2 as <your second select>;
alter table tmp2 add <some index to accelerate your join later>;

然后，您可以应用简单的联接来获得最终结果：

select tmp1.id, tmp1.name, tmp1.address, tmp2.occupation
    from tmp1 inner join tmp2 using (id)
    order by tmp1.id;

另一种方法是使用VIEW，但由于索引不是他们所拥有的最好的东西，我会避免它们，特别是当你的前两个select复杂时。

Answer 3

这些（临时表，加入两个结果集）都不是必需的。

直接从源表中编写查询会好得多。不仅仅是出于性能原因（1个查询明显优于2个加入的查询加上1个），但是为了您的理解和进步。

Answer 4

我强烈建议发布您的SQL，以便实现正确的解决方案。也就是说你应该用MySQL而不是PHP来做这件事。

但是，您需要遍历第一组记录并构建一个数组。然后遍历第二个，将其附加到id匹配的第一个集合。

Answer 5

从

开始

SELECT tablea.id,tablea.name,tablea.address,tableb.occupation

并在WHERE子句中添加类似的内容：

WHERE tablea.id = tableb.id

我认为你不需要左连接。

加入mysql的两个查询结果

真实世界示例

第一个查询

第二个查询

数据库

5 个答案: