我正在尝试将一些原始 SQL 迁移到模型上的 Eloquent(或查询生成器)范围。我的零件历史记录表如下所示:
+----+---------+--------+------------+
| id | part_id | status | created_at |
+----+---------+--------+------------+
| 1 | 1 | 1 | ... |
| 2 | 1 | 2 | ... |
| 3 | 2 | 1 | ... |
| 4 | 1 | 2 | ... |
| 5 | 2 | 2 | ... |
| 6 | 1 | 3 | ... |
请注意,相同的 part_id 可以有多个状态相同的条目。
目前我使用以下内容来选择最新状态:
$part = Part::leftjoin( DB::raw("
(SELECT t1.part_id, ph.status, t1.part_status_at
FROM (
SELECT part_id, max(created_at) part_status_at
FROM part_histories
GROUP BY part_id) t1
JOIN part_histories ph ON ph.part_id = t1.part_id AND t1.part_status_at = ph.created_at) as t2
)", 't2.part_id', '=', 'parts.id')->where( ... )
我试图在零件模型上制作一个范围,到目前为止我有这个:
public function scopeWithLatestStatus($query)
{
return $query->join(DB::raw('part_histories ph'), function ($join) {
$join->on('ph.part_id', '=', 't1.id')->on('t1.part_status_at', '=', 'ph.created_at');
})
->from(DB::raw('(select part_id as id, max(created_at) part_status_at from part_histories GROUP BY part_id) t1'))
->select('t1.id', 'ph.part_status', 't1.part_status_at');
}
这是其中的一部分(但仍在使用一些原始 SQL),我无法弄清楚其余部分
您可以将查询重写为左连接以获得相同的结果
select a.*
from part_histories a
left join part_histories b on a.part_id = b.part_id
and a.created_at < b.created_at
where b.part_id is null
我想你可以在你的范围内轻松转换上面的查询,比如
public function scopeWithLatestStatus($query)
{
return $query->leftJoin('part_histories as b', function ($join) {
$join->on('a.part_id', '=', 'b.part_id')
->where('a.created_at', '<', 'b.created_at');
})
->whereNull('b.part_id')
->from('part_histories as a')
->select('a.*');
}
Laravel Eloquent 选择最大 created_at 的所有行
使用上述查询作为has
关系进行编辑,要获取每个部分的最新历史记录,您可以定义一个hasOne
关系,如
namespace App\Models;
use Illuminate\Database\Eloquent\Model;
use Illuminate\Support\Facades\DB;
class Part extends Model
{
public function latest_history()
{
return $this->hasOne(\App\Models\PartHistory::class, 'part_id')
->leftJoin('part_histories as p1', function ($join) {
$join->on('part_histories.part_id', '=', 'p1.part_id')
->whereRaw(DB::raw('part_histories.created_at < p1.created_at'));
})->whereNull('p1.part_id')
->select('part_histories.*');
}
}
然后要加载具有最新历史记录的零件,您可以将上面定义的映射加载为
$parts = Part::with('latest_history')->get();
您将拥有一份零件清单以及最新的历史记录
Array
(
[0] => Array
(
[id] => 1
[title] => P1
[latest_history] => Array
(
[id] => 6
[created_at] => 2018-06-16 08:25:10
[status] => 1
[part_id] => 1
)
)
....
)
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