如何在Laravel 5.3中创建与表的两次连接的查询? [英] How to create query with twice a connection to a table in Laravel 5.3?
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问题描述
我需要通过一个查询获得两个城市名称:
I need get two city names with one query:
例如:
城市表:
+---------+----------+
| Pana | Name |
+---------+----------+
| THR | Tehran |
| LON | London |
+---------+----------+
在模型中: from_city 是 THR ,而 to_city 是 LON
public function scopePrintQuery($query, $id)
{
$join = $query
-> join('cities', 'cities.pana', 'flights.from_city')
-> join('cities', 'cities.pana', 'flights.to_city')
-> where('flights.id', $id)
->get([
'flights.*',
'cities.name as from_city'
??? for to_city?
]);
return $join;
}
现在,我需要在此查询中获得 from_city 名称和 to_city 名称.
Now, I need get from_city name and to_city name in this query.
该查询不适用于一个表中的两个联接!
The query does not work with two joins from one table!
如何创建此查询?
推荐答案
使用直接SQL,您可以为每个联接表赋予别名-例如
With straight SQL you could give each joined table an alias - e.g.
SELECT flights.*
FROM flights as f
JOIN cities as fromCity on fromCity.pana = f.from_city
JOIN cities as toCity on toCity.pana = f.to_city
WHERE f.id = 3 --
对于Eloquent,使用 select()指定选择字段.也可以使用 DB :: raw()来使用原始SQL(例如,表的别名,如DB::raw('cities as toCity')
.
With Eloquent, use select() to specify select fields. Also use DB::raw() to use raw SQL (e.g. giving an alias to table like DB::raw('cities as toCity')
.
public function scopePrintQuery($query, $id)
{
$join = $query
-> join(DB::raw('cities as fromCity'), 'fromCity.pana', 'flights.from_city')
-> join(DB::raw('cities as toCity'), 'toCity.pana', 'flights.to_city')
-> where('flights.id', $id)
->select([
'flights.*',
DB::raw('fromCity.name as from_city')
DB::raw('toCity.name as to_city')
]);
return $join->get();
}
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