Laravel HasMany跨多个连接

问题描述

我想在第二张表offer_related上检索与Offer相关的Offer，因为我无法更改Offer表的架构.

I want to retrieve Offers related to Offer on a second table offer_related because I can't change the schema of the Offer table.

我在不同的连接上有两个数据库，一个在offers上，另一个在offer_related上.

I have two databases on different connections, offers on one, and offer_related on another.

为了争辩，在示例中，为清楚起见，我将为数据库命名的方式如下:哪些可以更改，哪些不能更改.

For the sake of argument, I'm going to name databases as follows for clarity in my examples with regards to which can change and which can't.

包含offers的
• 数据库此后称为immutable
包含offer_related的
• 数据库此后称为mutable

• database containing offers henceforth known as immutable
• database containing offer_related henceforth known as mutable

示例架构如下

connection1.mutable.offer_related

offer_id | related_offer_id
---------------------------
1        | 2
1        | 3

connection2.immutable.offers

id | name
---------------------------
1  | foo
2  | bar
3  | baz

我假设这将是一个belongsToMany关系，但是我似乎无法正确理解.

I'm assuming it'd be a belongsToMany relationship, but I can't seem to get it right.

return $this->belongsToMany(Offer::class, 'immutable.offer', 'id');

// Syntax error or access violation: 1066 Not unique table/alias: 'offer'

我还尝试过使用自定义查询手动建立一个AboutToMany关系，但没有成功.

I've also tried to manually build out a belongsToMany relationship with a custom query with no success.

我想可以打电话

Offer::find(1)->related; // Offer(2), Offer(3)

推荐答案

将关系更改为:

    return $this->belongsToMany(Offer::class, 'mutable.offer_related',
                                'offer_id', 'related_offer_id');

您的原始查询尝试建立关系而不使用关系表(offer_related).那是问题.

Your original query was trying to establish a relationship without using the relation table (offer_related). That is the problem.

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