Laravel 5.2。数据库表+加入更新

Question

我需要表目录中的更新键，并编写查询（mysql查询正确）：

```
update attributes a inner join catalog c on a.parent_id = c.id set a.key = c.left_key
```
and with Laravel DB:
```
DB::table('attributes as a')
    ->join(catalog as c', 'a.parent_id', '=', 'c.id')
    ->update([ 'a.key' => 'c.left_key' ]);
```
It's right query, but DB::table ... make all key in table catalog to 0.
I write 
```
DB::statement('update attributes a inner join catalog c on a.parent_id = c.id set a.key = c.left_key;');
```

它的工作！但我不明白为什么带有连接和更新的DB :: table无法正常工作

Answer 1

您可以尝试：

DB::table('attributes as a')
   ->join('catalog as c', 'a.parent_id', '=', 'c.id')
   ->update([ 'a.key' => DB::raw("`c`.`left_key`") ]);