问题描述

CREATE TABLE IF NOT EXISTS `messages` (
  `id` int(11) unsigned NOT NULL auto_increment,
  `user_id` int(11) unsigned NOT NULL,
  `node_id` int(11) unsigned NOT NULL,
  `reciever_id` int(11) unsigned NOT NULL,
  `created` datetime default NULL,
  `modified` datetime default NULL,
  PRIMARY KEY  (`id`)
) ENGINE=InnoDB  DEFAULT CHARSET=utf8 AUTO_INCREMENT=9 ;

INSERT INTO `messages` (`id`, `user_id`, `node_id`, `reciever_id`, `created`, `modified`) VALUES
(1, 1, 1, 15, '2011-12-07 00:00:00', '2011-12-07 02:00:00'),
(2, 15, 1, 1, '2011-12-07 02:00:00', '2011-12-07 02:00:00'),
(3, 15, 2, 1, '2011-12-07 11:00:00', '2011-12-07 11:00:00'),
(4, 1, 2, 15, '2011-12-07 11:00:00', '2011-12-07 11:00:00'),
(5, 1, 3, 18, '2011-12-07 11:00:00', '2011-12-07 11:00:00'),
(6, 18, 3, 1, '2011-12-07 11:00:00', '2011-12-07 11:00:00'),
(7, 1, 4, 18, '2011-12-07 12:00:00', '2011-12-07 12:00:00'),
(8, 18, 4, 1, '2011-12-07 12:00:00', '2011-12-07 12:00:00');


CREATE TABLE IF NOT EXISTS `nodes` (
  `id` int(11) unsigned NOT NULL auto_increment,
  `message` text NOT NULL,
  `author_id` int(11) unsigned NOT NULL,
  `read` tinyint(1) default NULL,
  `created` datetime default NULL,
  `modified` datetime default NULL,
  PRIMARY KEY  (`id`)
) ENGINE=InnoDB  DEFAULT CHARSET=utf8 AUTO_INCREMENT=5 ;

INSERT INTO `nodes` (`id`, `message`, `author_id`, `read`, `created`, `modified`) VALUES
(1, 'Hi! How are you ? dude wanna meet up this weekend ?', 1, 0, '2011-12-07 02:00:00', '2011-12-07 02:00:00'),
(2, 'Sure. wanna go to Mangalore Pearl to eat Neer Dosa..', 15, 0, '2011-12-07 11:00:00', '2011-12-07 11:00:00'),
(3, 'Hi How are u Buddy ? Long time no see...', 1, 0, '2011-12-07 11:00:00', '2011-12-07 11:00:00'),
(4, 'yeah. are you back in town ? i think we should meet up man. its been ages ....', 18, 0, '2011-12-07 12:00:00', '2011-12-07 12:00:00');


CREATE TABLE IF NOT EXISTS `users` (
  `id` int(11) unsigned NOT NULL auto_increment,
  `first_name` varchar(255) default NULL,
  `last_name` varchar(255) default NULL,
  `email` varchar(255) default NULL,
  `password` varchar(40) default NULL,
  `username` varchar(255) default NULL,
  `birthday` date default NULL,
  `gender` varchar(255) default NULL,
  `city_id` int(11) unsigned NOT NULL,
  `status` varchar(255) NOT NULL,
  `created` datetime default NULL,
  `modified` datetime default NULL,
  PRIMARY KEY  (`id`)
) ENGINE=InnoDB  DEFAULT CHARSET=utf8 AUTO_INCREMENT=21 ;

我正在尝试在 Cake 中创建一个子查询.但不知道如何开始:(

I am trying to create a subquery in Cake. but not sure how to start :(

这是我要执行的 SQL

This is the SQL i want to execute

SELECT *
FROM (

SELECT *
FROM messages AS msg
WHERE user_id =1
ORDER BY modified DESC
) AS latest_message
GROUP BY reciever_id

使用子查询好还是写SQL语句好?

Is it better to use sub Queries or write SQL statement ?

推荐答案

既然您试图按接收者分组，那么为什么不更改查询以检索接收者，然后检索属于每个接收者的消息呢?下面，我假设使用了可包含的行为.

Since you are trying to group by the receiver, then why not alter the query to retrieve the receivers and then the messages that belong to each one? Below, I am assuming use of the containable behavior.

$this->Receiver->find('all', array(
    'contain' => array(
        'Message' => array(
            'conditions' => array('Message.user_id' => 1),
            'order' => array('Message.modified' => 'DESC'),
        )
    )
));

编辑

根据您的评论，我添加了此查询以查看是否有帮助.

I added this query to see if it helps based on your comment.

$this->Message->find(
    'all',
    array(
        'conditions' => array('Message.user_id' => 1),
        'fields' => array('Message.*', 'MAX(Message.modified) as max_mod'),
        'group' => 'Message.receiver_id'
    )
);

这篇关于来自 SQL 的 CakePHP 子查询的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持编程学习网！