Php 在Laravel中创建子查询-查询生成器
我尝试创建一个子查询。目前,我的两个问题是:Php 在Laravel中创建子查询-查询生成器,php,laravel,laravel-5,eloquent,query-builder,Php,Laravel,Laravel 5,Eloquent,Query Builder,我尝试创建一个子查询。目前,我的两个问题是: select `key` from messages group by `key`; 及 目的是突出显示我的表消息所有按键分组的元素,并保留最后一个元素(在desc创建) 谢谢你像这样的方法应该会奏效: $data = DB::table('messages')->whereIn('key',function($q) { $q->select('key')->from('messages')->groupBy('ke
select `key` from messages group by `key`;
及
目的是突出显示我的表消息
所有按键分组的元素,并保留最后一个元素(在desc创建)
谢谢你像这样的方法应该会奏效:
$data = DB::table('messages')->whereIn('key',function($q) {
$q->select('key')->from('messages')->groupBy('key');
})->latest()->take(1)->get();
你可以用两种不同的方法来做这件事 查询生成器:
DB::table('messages AS a')
->leftJoin('messages AS b', function($join) {
$join->on('a.created_at', '<', 'b.created_at');
$join->on('a.key', '=', 'b.key');
})
->groupBy(['a.key', 'a.message', 'a.created_at'])
->havingRaw('COUNT(b.key) < 1')
->select(['a.key', 'a.message', 'a.created_at'])
->get();
如果我们假设你们有这样的桌子
postgres=# select * from messages;
id | key | message | created_at
----+---------+------------------------+----------------------------
1 | contact | send from contact page | 2015-10-31 19:45:16.850698
2 | contact | contact page message | 2015-10-31 19:45:34.417231
3 | product | product 1 | 2015-10-31 19:45:44.49584
4 | product | product 2 | 2015-10-31 19:45:46.856691
5 | contact | hello it is me | 2015-10-31 18:45:35.801967
6 | about | who are you | 2015-10-31 19:46:04.123369
7 | product | product 3 | 2015-10-31 19:46:12.414364
8 | about | hi guys | 2015-10-31 19:46:18.23442
(8 rows)
对于两个不同的查询,结果如下
postgres=# select key, message, created_at from (select key, message, created_at, rank() over (partition by key order by created_at desc) as rank from messages) foo where rank = 1;
key | message | created_at
---------+----------------------+----------------------------
about | hi guys | 2015-10-31 19:46:18.23442
contact | contact page message | 2015-10-31 19:45:34.417231
product | product 3 | 2015-10-31 19:46:12.414364
(3 rows)
它不起作用,因为它引用了那个录音。我给你拍了一张我所拥有的东西的快照。谢谢你,还有
postgres=# select * from messages;
id | key | message | created_at
----+---------+------------------------+----------------------------
1 | contact | send from contact page | 2015-10-31 19:45:16.850698
2 | contact | contact page message | 2015-10-31 19:45:34.417231
3 | product | product 1 | 2015-10-31 19:45:44.49584
4 | product | product 2 | 2015-10-31 19:45:46.856691
5 | contact | hello it is me | 2015-10-31 18:45:35.801967
6 | about | who are you | 2015-10-31 19:46:04.123369
7 | product | product 3 | 2015-10-31 19:46:12.414364
8 | about | hi guys | 2015-10-31 19:46:18.23442
(8 rows)
postgres=# select key, message, created_at from (select key, message, created_at, rank() over (partition by key order by created_at desc) as rank from messages) foo where rank = 1;
key | message | created_at
---------+----------------------+----------------------------
about | hi guys | 2015-10-31 19:46:18.23442
contact | contact page message | 2015-10-31 19:45:34.417231
product | product 3 | 2015-10-31 19:46:12.414364
(3 rows)