将两个gorm查询转换为一个

Question

我有以下型号

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
    ...
}

我试图通过名称和组名称获得一个实例。

我可以用下面的代码来做

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。对如何实现这一点有什么想法吗？

Answer 1

您始终可以使用Joins函数进行SQL连接。大概是这样的：

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
}