英文:
Gorm Golang fetching a collection and its relationships
问题
最近我开始使用Golang，并决定尝试使用GORM作为ORM。它在大多数情况下运行得很好，但像大多数ORM一样，有时候它有一些限制。幸运的是，它与database/sql非常紧密地结合在一起，所以我可以轻松地进行自定义查询。
我想知道在gorm中是否有其他方法可以实现这个功能：
我有一个名为Companies的结构体，Companies与emails、addresses和phones之间是一对多的关系。我在gorm中使用以下代码来获取公司列表及其相应的信息。我使用了gorm的Preload函数。
db.DBAccess.
Model(&companies).
Count(&dbInfo.Count).
Order("companies.id asc").
Offset(offset).
Limit(length).
Preload("Addresses").
Preload("Phones").
Preload("Emails").
Find(&companies)
这个方法完全正常工作。然而，我觉得可能还有其他方法可以在没有Preload函数的情况下实现这个功能。有什么想法吗？
英文:
I recently started using Golang and decided to give GORM a try as an ORM.
It works pretty well on most things, but as most ORMs are sometimes it's limited. Luckily it ties very well into database/sql so I can do custom queries easily.
I'm wondering if there is any other way to do this in gorm:
I have a struct Companies, Companies have one to many relationships w/ emails, addresses, and phones. I use the following code in gorm to pull a list of companies and their corresponding info. I use gorm's Preload function.
db.DBAccess.
Model(&companies).
Count(&dbInfo.Count).
Order("companies.id asc").
Offset(offset).
Limit(length).
Preload("Addresses").
Preload("Phones").
Preload("Emails").
Find(&companies)
This works perfectly fine. However I feel like there is another way to accomplish this without the Preload function. Any ideas?
答案1
得分: 2
你可以稍后加载相关实体（仅在需要时），使用DB.Related，如文档所示：
// 用户有多个电子邮件
db.Model(&user).Related(&emails)
//// SELECT * FROM emails WHERE user_id = 111;
// user_id是外键，111是用户主键的值
// 指定外键
db.Model(&user).Related(&emails, "ProfileId")
//// SELECT * FROM emails WHERE profile_id = 111;
// profile_id是外键，111是用户主键的值
我在文档中没有看到其他方法。
英文:
You can load the related entities later (only when/if needed), using DB.Related as shown in the documentation :
// User has many emails
db.Model(&user).Related(&emails)
//// SELECT * FROM emails WHERE user_id = 111;
// user_id is the foreign key, 111 is user's primary key's value
// Specify the foreign key
db.Model(&user).Related(&emails, "ProfileId")
//// SELECT * FROM emails WHERE profile_id = 111;
// profile_id is the foreign key, 111 is user's primary key's value
I do not see another way in the documentation.
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