laravel eloquent 查询组按最后一个 id
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laravel eloquent query group by last id
提问by Lucas Campos
Hi I'm trying to get the last register in DB for each equipment
嗨，我正在尝试为每个设备获取 DB 中的最后一个寄存器
I got like
我喜欢
id | id_equip
-----+----------
1 | 3
2 | 3
3 | 3
4 | 2
5 | 2
I want to query like the last id of each equip like:
我想像每个装备的最后一个 id 一样查询：
id | id_equip
-----+----------
3 | 3
5 | 2
I tried this:
我试过这个：
$calibracao = $this->calibracao->orderBy('id', 'DESC')->groupBy('id_equip')->get();
thanks for the help!
谢谢您的帮助！
回答by damiani
A simple way, without join, using max:
一个简单的方法，不用join，使用max：
$query = DB::table('equip')
->select(DB::raw('*, max(id) as id'))
->groupBy('id_equip')
->orderBy('id', 'asc')
->get();
(Assuming, of course, that you can count on your idto be in date order.)
（当然，假设您可以指望按id日期顺序排列。）
You can also do this with Eloquent, using a self-referencing one-to-one relationship. The query takes longer, but it's much more Laravel-like:
你也可以使用 Eloquent来做到这一点，使用自引用的一对一关系。查询需要更长的时间，但它更像 Laravel：
Define the relationship in your model:
定义模型中的关系：
class myModel extends Eloquent {
public function latestEquipment()
{
return $this->hasOne('myModel', 'id_equip', 'id_equip')->latest();
}
}
(Note that in this case, we're using latest()so that we don't rely on the order of ids to determine the most recent entry, but rather on the created_atdate of each record. This is more accurate.)
（请注意，在这种情况下，我们使用的是latest()这样我们不依赖于ids的顺序来确定最近的条目，而是created_at根据每条记录的日期。这样更准确。）
To retrieve all the records, with their latest equipment entry:
要检索所有记录及其最新设备条目：
$latest = myModel::with('latestEquipment')->groupBy('id_equip')->get();
// loop over the results
foreach ($latest as $l) {
if ($l->equipment) {
echo('ID: ' . $l->id . 'ID_EQUIP: ' . $l->id->id_equip . '<br>');
}
}
回答by Bogdan
I'm not sure if there's an easier way and this is kind of convoluted because of the join, but it should give the result you want:
我不确定是否有更简单的方法，由于 ，这有点令人费解join，但它应该给出您想要的结果：
DB::table('equip as e')
->select('e.*')
->join(DB::raw("(SELECT id_equip, MAX(id) id FROM equip GROUP BY id_equip) as _e"), function ($join) {
$join->on('e.id', '=', '_e.id')->on('e.id_equip', '=', '_e.id_equip');
})
->orderBy('id', 'asc')
->get();
回答by Lucas Campos
public function latest($equipamentos)
{
foreach ($equipamentos as $equip)
{
$latest[$equip->cod] = DB::table('tb_calibracao')
->where('cod_equipamento', $equip->cod)
->where('parecer', '1')
->orderBy('cod', 'Desc')
->first();
}
return $latest;
}
That worked, thx for the help!
那行得通，谢谢您的帮助！
