Video
-------
id
source_low
source_med
source_high
Source
--------
id
duration
thumbnail
视频项目可以包含至少1个或最多3个源(source low,source med,source high)。
这个想法与YouTube相同,也就是说一个视频记录可以包含多个质量。因此,当我返回持续时间/缩略图时,我想检查哪个源存在并返回其中之一。
例如,如果一个视频有source_low或source_med,那么意味着有source_low和source_med的持续时间和缩略图,然后我只需要返回其中的一个。
Codeigniter语法:
$this->db->select('v.*, sl.duration, sm.duration as duration_m, sh.duration as duration_h, sl.thumbnail, sm.thumbnail as thumbnail_m, sh.thumbnail as thumbnail_h');
$this->db->from('video as v');
$this->db->join('source as sl', 'v.source_low = sl.video_id', 'left');
$this->db->join('source as sm', 'v.source_med = sm.video_id', 'left');
$this->db->join('source as sh', 'v.source_high = sh.video_id', 'left');
$this->db->group_by('v.id');
SQL(获取缩略图的方式相同):
SELECT v.*, sl.duration, sm.duration as duration_sm, sh.duration as duration_sh
FROM video as v
LEFT JOIN source as sl ON (v.source_low = sl.video_id)
LEFT JOIN source as sm ON (v.source_med = sm.video_id)
LEFT JOIN source as sh ON (v.source_high = sh.video_id)
GROUP BY v.id;
现在我可以返回所有的结果,包括空值,但是如何只返回一个持续时间和一个缩略图?
谢谢你的帮助。
更新:
刚才更新了查询语句,但似乎 CodeIgniter 处理它时出现了一些错误,有什么想法吗?谢谢。
我的代码:
$this->db->select('v.*, COALESCE(b.duration, bt.duration, bc.duration) AS duration, COALESCE(b.thumbnail, bt.thumbnail, bc.thumbnail) AS thumbnail');
在SQL中:
Error Number: 1064
You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'AS duration, COALESCE(b.thumbnail, `bt`.`thumbnail`, `bc`.`thumbnail)` AS thumbn' at line 1
SELECT `v`.*, `t`.`name`, `t`.`name_tw`, `t`.`name_cn`, COALESCE(b.duration, `bt`.`duration`, `bc`.`duration)` AS duration, COALESCE(b.thumbnail, `bt`.`thumbnail`, `bc`.`thumbnail)` AS thumbnail FROM (`video` as v) JOIN `teacher` as t ON `v`.`teacher_id` = `t`.`id` LEFT JOIN `brightcove` as b ON `v`.`video` = `b`.`video_id` LEFT JOIN `brightcove` as bt ON `v`.`video_tw` = `bt`.`video_id` LEFT JOIN `brightcove` as bc ON `v`.`video_cn` = `bc`.`video_id` WHERE `v`.`is_delete` = 0 AND `v`.`type` = 0 GROUP BY `v`.`id` ORDER BY `v`.`start_date` desc
php
字符串中,所以很难调试。去掉它们,只显示SQL语句,我们就能够提供帮助了! - LondonRobv.*, COALESCE(...
,但是在错误信息中却出现了t.name
、t.name_tw
等。 - vhu