在PHP3中,如何在Group by之前执行Order by?
我正在获取用户给出的所有答案。但我只需要用户的最新回答/响应(使用响应id)。我正在运行下面的查询在PHP3中,如何在Group by之前执行Order by?,php,cakephp,cakephp-3.0,greatest-n-per-group,Php,Cakephp,Cakephp 3.0,Greatest N Per Group,我正在获取用户给出的所有答案。但我只需要用户的最新回答/响应(使用响应id)。我正在运行下面的查询 $users_all_answers=$this->SurveySectionAnswers->find('all') ->where(['survey_response_id IN'=>$response_ids]) ->order(['survey_
$users_all_answers=$this->SurveySectionAnswers->find('all')
->where(['survey_response_id IN'=>$response_ids])
->order(['survey_response_id'=>'desc'])
->group(['survey_question_id'])
->hydrate(false)
->toArray();
但我得到的是用户的答案,而不是最新的响应,因为在Order by之前在Group by上执行。那么,有什么解决方案可以让我通过用户的最新响应获得所有答案呢
得到这样的数组
[0] => Array
(
[id] => 527
[survey_response_id] => 74
[survey_question_id] => 84
[survey_answer] =>
[survey_score] => 0
[survey_section_id] => 50
[survey_answer_id] => 138
[completed] => 1
)
[1] => Array
(
[id] => 528
[survey_response_id] => 74
[survey_question_id] => 85
[survey_answer] =>
[survey_score] => 0
[survey_section_id] => 48
[survey_answer_id] => 142
[completed] => 1
)
但是我想要像
[0] => Array
(
[id] => 527
[survey_response_id] => 76
[survey_question_id] => 84
[survey_answer] =>
[survey_score] => 0
[survey_section_id] => 50
[survey_answer_id] => 138
[completed] => 1
)
[1] => Array
(
[id] => 528
[survey_response_id] => 76
[survey_question_id] => 85
[survey_answer] =>
[survey_score] => 0
[survey_section_id] => 48
[survey_answer_id] => 142
[completed] => 1
)
在MySQL中,GROUPBY在ORDERBY之前执行。GROUP BY将始终选择结果集中的第一行,因此在执行该分组之前,它不受ORDER BY的影响 在MySQL中,有一种方法可以实现您所描述的功能。我更喜欢使用这样一种方法,即以确保最新的行是实际选中的行的方式将表连接到自身 在CakePHP中,它看起来像:
$users_all_answers = $this->SurveySectionAnswers->find()
->join([
'SurveySectionAnswers_2' => [
'table' => 'survey_section_answers',
'type' => 'LEFT',
'conditions' => [
'SurveySectionAnswers_2.survey_question_id' => new \Cake\Database\Expression\IdentifierExpression('SurveySectionAnswers_2.survey_question_id'),
'SurveySectionAnswers.id <' => 'SurveySectionAnswers_2.id'
]
]
])
->where([
'SurveySectionAnswers.survey_response_id IN' => $response_ids,
'SurveySectionAnswers_2 IS ' => null
])
->hydrate(false)
->toArray();
$users\u all\u answers=$this->SurveySectionAnswers->find()
->加入([
‘SurveySectionAnswers_2’=>[
“表”=>“调查部分答案”,
'类型'=>'左',
“条件”=>[
“SurveySectionAnswers\u 2.survey\u question\u id”=>new\Cake\Database\Expression\IdentifierExpression(“SurveySectionAnswers\u 2.survey\u question\u id”),
'SurveySectionAnswers.id另一种选择是使用或groupBy
这将对性能产生影响,但在代码中可能更清晰
获取答案列表。这将返回一个带有集合接口的对象
$users_all_answers = $this->SurveySectionAnswers->find('all')
->where(['survey_response_id IN'=>$response_ids])
->order(['survey_response_id'=>'asc'])
->hydrate(false);
需要注意的是,您必须以相反的顺序对查询进行排序,因为indexBy和groupBy将返回组中的最后一项
在上面的查询中,我将顺序survey\u response\u id
从desc
更改为asc
,以完成此操作
然后,您可以在有序查询中调用groupBy或indexBy。这将立即调用您的查询
$users_grouped_by_id = $users_all_answers->groupBy('survey_question_id')
或者,如果每个组只需要一个结果
$users_indexed_by_id = $users_all_answers->indexBy('survey_question_id')
groupBy
和indexBy
是集合接口函数。不要与group
相混淆,后者是查询生成器函数。每个查询都是集合,但集合不是查询。在mysql
中不能这样做,您可以使用max/min函数并将其与group-by函数混合,或者使用se子查询以获取最新答案,然后对其排序,或者在获取数据后使用php it self对其排序;