在使用GORM进行数据库操作时,我们常常会遇到一张表需要同时关联两个外键的情况。这种情况下,如何正确地设置和使用外键成为了一个需要解决的问题。在本文中,php小编鱼仔将为大家详细介绍如何使用GORM来处理一张表的两个外键,以及相关的注意事项和实际应用案例。通过学习本文,相信大家能够更好地理解和运用GORM进行数据库操作。
我想创建三个表:用户、事件、配对。
在配对表中将有三列:eventId、user1、user2。 所以user1、user2都会通过id引用Users表。
我知道如何在 sql 中执行此操作,但我想尝试使用 ORM。我已阅读文档,但我不知道如何做到这一点
type User struct { Id uint64 `gorm:"primarykey"` TGtag string IsActive bool } type RCEvent struct { Id uint64 `gorm:"primarykey"` DateStarted time.Time IsActive bool } type Pair struct { EventId uint64 UserID1 uint64 UserID2 uint64 }
我尝试用 gorm 标签做一些事情,比如这样,但没有成功:
type User struct { Id uint64 `gorm:"primarykey"` TGtag string IsActive bool } type RCEvent struct { Id uint64 `gorm:"primarykey"` DateStarted time.Time IsActive bool Pairs []Pair `gorm:"many2many:pair;"` } type Pair struct { EventId uint64 `gorm:"primarykey"` UserID1 uint64 `gorm:"primarykey"` UserID2 uint64 `gorm:"primarykey"` }
另外,我尝试了类似的方法并遇到了运行时错误
type User struct { Id uint64 `gorm:"primarykey"` TGtag string IsActive bool } type RCEvent struct { Id uint64 `gorm:"primarykey"` DateStarted time.Time IsActive bool } type Pair struct { Event RCEvent User1 User //`gorm:"foreignkey:UserId"` User2 User //`gorm:"foreignkey:UserId"` }
[error] failed to parse value &db.Pair{Event:db.RCEvent{Id:0x0, DateStarted:time.Date(1, time.January, 1, 0, 0, 0, 0, time.UTC), IsActive:false}, User1:db.User{Id:0x0, TGtag:"", IsActive:false}, User2:db.User{Id:0x0, TGtag:"", IsActive:false}}, got error invalid field found for struct untitledPetProject/internal/db.Pair's field Event: define a valid foreign key for relations or implement the Valuer/Scanner interface
要使用另一个结构作为外键,您应该将其 id 添加为目标结构中的另一个字段,对于您的情况,这里是工作示例(使用 gorm 示例):
package main import ( "log" "time" "gorm.io/driver/sqlite" "gorm.io/gorm" ) type User struct { gorm.Model ID uint64 `gorm:"primarykey"` TGtag string IsActive bool } type RCEvent struct { gorm.Model ID uint64 `gorm:"primarykey"` DateStarted time.Time IsActive bool } type Pair struct { gorm.Model ID uint64 `gorm:"primarykey"` EventID uint64 Event RCEvent User1ID uint64 User1 User User2ID uint64 User2 User } func main() { db, err := gorm.Open(sqlite.Open("test.db"), &gorm.Config{}) if err != nil { panic("failed to connect database") } // Migrate the schema err = db.AutoMigrate(&User{}) if err != nil { log.Fatal(err) } err = db.AutoMigrate(&RCEvent{}) if err != nil { log.Fatal(err) } err = db.AutoMigrate(&Pair{}) if err != nil { log.Fatal(err) } // Create user1 := User{ID: 2, TGtag: "mohammad"} user2 := User{ID: 3, TGtag: "ali"} event := RCEvent{ID: 2} pair := Pair{ID: 2, EventID: 2, Event: event, User1ID: 2, User1: user1, User2ID: 3, User2: user2} db.Create(&user1) db.Create(&user2) db.Create(&event) db.Create(&pair) // Read var user User db.First(&user, 3) // find product with integer primary key db.First(&user, "t_gtag = ?", "ali") // find product with code D42 // Update - update product's price to 200 db.Model(&user).Update("is_active", false) // Update - update multiple fields db.Model(&user).Updates(User{ID: 4, TGtag: "ahmad"}) // non-zero fields db.Model(&user).Updates(map[string]interface{}{"Id": 5, "TGtag": "hasan"}) // Delete - delete product db.Delete(&user, 2) }
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