[英]How can I combine these two queries into one?
我正在為我的自定義論壇編寫腳本,該腳本確定自用戶上次訪問該板以來,是否在某個板中發布了新主題或回復。 我有兩個表:一個表存儲線程,另一個表存儲回復。 我可以通過左聯接輕松找到董事會中是否有任何新答復。 我想添加一點,以發現該板上是否有新線程。 我該怎么做?
我的桌子:
CREATE TABLE IF NOT EXISTS `forum_threads` (
`thread_id` int(15) NOT NULL AUTO_INCREMENT,
`board_id` int(15) NOT NULL,
`author_id` int(15) NOT NULL,
`updater_id` int(15) NOT NULL,
`title` text NOT NULL,
`content` text NOT NULL,
`date_posted` timestamp NOT NULL DEFAULT CURRENT_TIMESTAMP ON UPDATE CURRENT_TIMESTAMP,
`date_updated` timestamp NOT NULL DEFAULT '0000-00-00 00:00:00',
`views` int(15) NOT NULL,
`status` tinyint(1) NOT NULL,
`type` tinyint(1) NOT NULL COMMENT '0 normal, 1 sticky, 2 global.',
PRIMARY KEY (`thread_id`)
) ENGINE=InnoDB DEFAULT CHARSET=latin1;
CREATE TABLE IF NOT EXISTS `forum_messages` (
`message_id` int(15) NOT NULL AUTO_INCREMENT,
`thread_id` int(15) NOT NULL,
`author_id` int(15) NOT NULL,
`modifier_id` int(15) DEFAULT NULL,
`content` text NOT NULL,
`date_posted` timestamp NOT NULL DEFAULT CURRENT_TIMESTAMP ON UPDATE CURRENT_TIMESTAMP,
`date_modified` timestamp NULL DEFAULT NULL,
`status` tinyint(1) NOT NULL,
PRIMARY KEY (`message_id`)
) ENGINE=InnoDB DEFAULT CHARSET=latin1;
我的劇本:
$this->db->select('m.message_id, m.thread_id, m.date_posted, t.thread_id, t.board_id');
$this->db->from('forum_messages AS m');
$this->db->join('forum_threads AS t', 'm.thread_id = t.thread_id', 'left');
$this->db->where('t.board_id', $board_id);
$this->db->where('m.date_posted > "'.$last_mark['date_marked'].'"');
if($query_new_messages = $this->db->get()){
if($query_new_messages->num_rows() > 0){
$contains_new_posts = TRUE;
} else {
$contains_new_posts = FALSE;
}
}
實際查詢:
SELECT
m.message_id, m.thread_id, m.date_posted, t.thread_id, t.board_id
FROM (forum_messages AS m)
LEFT JOIN forum_threads AS t ON m.thread_id = t.thread_id
WHERE `t`.`board_id` = '10' AND `m`.`date_posted` > "2014-03-02 06:01:31"
PS:我在CodeIgniter中這樣做。
OR
條件將為您提供所需的數據:
SELECT
m.message_id, m.thread_id, m.date_posted, t.thread_id, t.board_id
FROM (forum_messages AS m)
LEFT JOIN forum_threads AS t ON m.thread_id = t.thread_id
WHERE `t`.`board_id` = '10'
AND (`m`.`date_posted` > "2014-03-02 06:01:31"
OR `t`.`date_posted` > "2014-03-02 06:01:31")
但是,您應該對此進行基准測試。 該解決方案可能不是非常優化。 您應該對兩個快速查詢進行基准測試-一個針對帖子,一個針對線程-與執行一個可能更慢的查詢。
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