Question

我有以下MySQL表：

CREATE TABLE IF NOT EXISTS `conversations` (
    `id` int(11) NOT NULL AUTO_INCREMENT,
    `user1_id` int(11) NOT NULL,
    `user2_id` int(11) NOT NULL,
    PRIMARY KEY (`id`),
    UNIQUE KEY `user1_id_2` (`user1_id`,`user2_id`)
);

CREATE TABLE IF NOT EXISTS `messages` (
    `id` int(11) NOT NULL AUTO_INCREMENT,
    `conversation_id` int(11) NOT NULL,
    `sender_id` int(11) NOT NULL,
    `recipient_id` int(11) NOT NULL,
    `subject` varchar(64) NOT NULL,
    `body` text NOT NULL,
    `created` datetime DEFAULT NULL,
    `is_deleted_by_sender` tinyint(3) unsigned NOT NULL DEFAULT '0',
    `is_deleted_by_recipient` tinyint(3) unsigned NOT NULL DEFAULT '0',
    PRIMARY KEY (`id`)
);

注意：在会话表中，user1_id小于或等于user2_id。

我想获取用户X的会话列表，其中每个会话由该对话中用户X尚未删除的最后一条消息显示，并对结果进行分页。（就像facebook消息一样。无论X或其他用户发送了最后一条消息，它都显示为显示消息。

我来到了group-wise maximum solution，它帮助我创建了以下子查询：

SELECT MAX(SubTable.id) AS id, conversation_id 
FROM newtravel.messages AS SubTable
WHERE (
((SubTable.sender_id = 9) AND (SubTable.is_deleted_by_sender = 0))
OR 
((SubTable.recipient_id = 9) AND (SubTable.is_deleted_by_recipient = 0))
)
GROUP BY conversation_id

我们可以在$ this-＆gt; Paginator-＆gt;设置数组中将此子查询用作连接表吗？如果答案是肯定的，它应该生成如下查询：

SELECT m1.id, m1.conversation_id, m1.body, m1.sender_id, m1.recipient_id
FROM messages m1
INNER JOIN ( THE_SUB_QUERY_ABOVE ) m2 
ON ( m1.conversation_id = m2.conversation_id
AND m1.id = m2.id ) 
ORDER BY m1.id DESC

此最终查询返回所需结果。但我无法找到在PaginatorComponent中设置正确选项的方法。官方文档不足以进行此类查询。那么，在这种情况下我们如何配置查找条件，联接，子查询等？

Answer 1

好的。我已经解决了这个问题如下：

$this->Message->Behaviors->attach('Containable');

$conditionsSubQuery = array(
    'OR' => array(
        array(
            'SubTable.sender_id' => $this->Auth->user('id'),
            'SubTable.is_deleted_by_sender' => 0
        ),
        array(
            'SubTable.recipient_id' => $this->Auth->user('id'),
            'SubTable.is_deleted_by_recipient' => 0
        )
    )
);

$db = $this->Message->getDataSource();
$subQuery = $db->buildStatement(
        array(
    'fields' => array('MAX(id)'),
    'table' => $db->fullTableName($this->Message),
    'alias' => 'SubTable',
    'limit' => null,
    'offset' => null,
    'joins' => array(),
    'conditions' => $conditionsSubQuery,
    'order' => null,
    'group' => 'conversation_id',
        ), $this->Message
);

$subQuery = ' Message.id IN (' . $subQuery . ') ';

$this->Paginator->settings = array(
    'Message' => array(
        'limit' => 5,
        'maxLimit' => 5,
        'contain' => array(
            'Sender' => array(
                'id', 'name', 'is_online', 'profile_image', 'thumbnail'
            ),
            'Recipient' => array(
                'id', 'name', 'is_online', 'profile_image', 'thumbnail'
            ),
            'Conversation'
        ),
        'order' => 'Message.id DESC'
    )
);

$this->set('conversations', $this->Paginator->paginate('Message', $subQuery));

请注意，“消息”属于“发件人”和“收件人”，它们是“用户”表的别名。

Facebook喜欢CakePHP 2.1中的对话列表（与分组最大，子查询，连接相关）

1 个答案: