将两个gorm查询合并为一个

Question

我有以下模型

type Instance struct {
gorm.Model
Name               string `gorm:"index:idx_name_and_group,unique"`
UserID             uint
GroupID            uint `gorm:"index:idx_name_and_group,unique"`
...
}
type Group struct {
gorm.Model
Name                 string `gorm:"unique;"`
Instances            []Instance
...
}

我正在尝试通过名称和组名获取实例。

我可以使用下面的代码

func (r instanceRepository) FindByName(groupName string, instanceName string) (*model.Instance, error) {
var instance *model.Instance
var group *model.Group
err := r.db.
First(&group, "name = ?", groupName).Error
if err != nil {
return nil, err
}
err = r.db.
Where("name = ? and group_id = ?", instanceName, group.ID).
First(&instance).Error
return instance, err
}

但是我想把它变成一个查询。有什么想法吗?

Answer 1

始终可以使用Joins函数进行SQL连接。像这样:

func (r instanceRepository) FindByName(groupName string, instanceName string) (*model.Instance, error) {
var instance *model.Instance
err := r.db.
Joins("INNER JOIN groups g ON g.id = instances.group_id").
Where("g.name = ? AND instances.name = ?", groupName, instanceName).
First(&instance).Error
if err != nil {
return nil, err
}
return instance, err
}