[英]MySQL Many to Many Grouping
我有具有这些属性的下表:
位置 -location_id,名称
时间表 -schedule_id,名称
locatoin_schedule -location_id,schedule_id
我正在使用这样的查询。
SELECT l.name as locationName, s.name as scheduleName
FROM location AS l, schedule AS s, location_schedule AS ls
WHERE ls.schedule_id = s.schedule_id
AND ls.location_id = l.location_id
这将返回一个看起来像这样的数组:
Array
(
[0] => stdClass Object
(
[locationName] => testing
[scheduleName] => New Schedule
)
[1] => stdClass Object
(
[locationName] => another
[scheduleName] => New Schedule
)
[2] => stdClass Object
(
[locationName] => testing
[scheduleName] => Another Schedule
)
)
如果某个位置具有多个计划表(如testing
位置那样),则是否可以返回计划表的多维数组? 因此,我的预期结果将是仅包含2个索引的数组,而不是3个索引...但是测试locationName将包含具有两个调度的数组。
我希望这是有道理的,谢谢您的回答。
您将无法将当前查询处理到所需的数据结构中,或者使用GROUP_CONCAT然后将日程表字符串拆分成所需的结构。 我坚持使用第一个,因为它更干净并且查询速度更快。
$q="
SELECT l.name as locationName, s.name as scheduleName
FROM location AS l JOIN schedule AS s ON ls.schedule_id = s.schedule_id
JOIN location_schedule AS ls
ON ls.location_id = l.location_id";
$r=$db->query($q)
while($arr=$r->fetch_assoc()){
$data[$arr['locationName']][]=$arr['scheduleName'];
}
或GROUP_CONCAT选项:
$q="
SELECT l.name as locationName, GROUP_CONCAT(s.name) as scheduleName
FROM location AS l JOIN schedule AS s ON ls.schedule_id = s.schedule_id
JOIN location_schedule AS ls
ON ls.location_id = l.location_id
GROUP BY locationName";
$r=$db->query($q)
while($arr=$r->fetch_assoc()){
$schedules=explode($arr['scheduleName']);
$data[$arr['locationName']]=$schedules
}
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