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开发建设网站百度的广告推广需要多少费用

news 2025/7/21 17:09:49

开发建设网站,百度的广告推广需要多少费用,网站如何添加二维码,顺企网官网下载安装一对多的添加有两种情况： 一种是添加用户的时候同时创建文章其次是创建文章关联已经存在的用户。 package mainimport ("gorm.io/driver/mysql""gorm.io/gorm" )// User 用户表一个用户拥有多篇文章 type User struct {ID int64Name …

一对多的添加有两种情况：

一种是添加用户的时候同时创建文章
其次是创建文章关联已经存在的用户。

package mainimport ("gorm.io/driver/mysql""gorm.io/gorm"
)// User 用户表 一个用户拥有多篇文章
type User struct {ID       int64Name     string    `gorm:"size:6"`Articles []Article //用户拥有的文章列表 has many
}type Article struct {ID     int64  `gorm:"size:4"`Title  string `gorm:"size:16"`UserID int64  //属于  belongs to
}func (*User) TableName() string {return "user"
}func (*Article) TableName() string {return "article"
}func main() {dsn := "root:7PXjAkY!&nlR@tcp(192.168.11.128:3306)/test?charset=utf8mb4&parseTime=True&loc=Local"db, _ := gorm.Open(mysql.Open(dsn), &gorm.Config{})db.Debug().AutoMigrate(&User{}, &Article{})var u Usera1 := Article{Title: "redis",}u = User{Name: "yanzi",Articles: []Article{{Title: "golang",},{Title: "k8s",},a1,},}db.Debug().Create(&u)
}[8.981ms] [rows:3] INSERT INTO `article` (`title`,`user_id`) VALUES ('golang',2),('k8s',2),('redis',2) ON DUPLICATE KEY UPDATE `user_id`=VALUES(`user
_id`)[14.812ms] [rows:1] INSERT INTO `user` (`name`) VALUES ('yanzi')

最后一种就是关联已有用户

	var articles []Articlearticles = []Article{{Title:  "cherry",UserID: 2,},{Title:  "marry",UserID: 2,},}db.Debug().Create(&articles)[11.754ms] [rows:2] INSERT INTO `article` (`title`,`user_id`) VALUES ('cherry',2),('marry',2)

外键添加

	var u Userdb.Debug().Take(&u, 3)var a Articledb.Debug().Take(&a, 7)u.Articles = []Article{a}db.Debug().Save(&u)[1.300ms] [rows:1] SELECT * FROM `user` WHERE `user`.`id` = 3 LIMIT 1[1.629ms] [rows:1] SELECT * FROM `article` WHERE `article`.`id` = 7 LIMIT 1[2.901ms] [rows:2] INSERT INTO `article` (`title`,`user_id`,`id`) VALUES ('marry',3,7) ON DUPLICATE KEY UPDATE `user_id`=VALUES(`user_id`)[6.363ms] [rows:0] UPDATE `user` SET `name`='test' WHERE `id` = 3[0.557ms] [rows:0] INSERT INTO `article` (`title`,`user_id`,`id`) VALUES ('marry',3,7) ON DUPLICATE KEY UPDATE `user_id`=VALUES(`user_id`)[3.713ms] [rows:0] INSERT INTO `user` (`name`,`id`) VALUES ('test',3) ON DUPLICATE KEY UPDATE `name`=VALUES(`name`)mysql> select * from user;
+----+-------+
| id | name  |
+----+-------+
|  1 | lucas |
|  2 | yanzi |
|  3 | test  |
+----+-------+
mysql> select * from article;
+----+--------+---------+
| id | title  | user_id |
+----+--------+---------+
|  1 | golang |       1 |
|  2 | k8s    |       1 |
|  3 | golang |       2 |
|  4 | k8s    |       2 |
|  5 | redis  |       2 |
|  6 | cherry |       2 |
|  7 | marry  |       3 |
+----+--------+---------+

	var u Userdb.Debug().Take(&u, 3)var a Articledb.Debug().Take(&a, 6)db.Debug().Model(&u).Association("Articles").Append(&a)[2.196ms] [rows:2] INSERT INTO `article` (`title`,`user_id`,`id`) VALUES ('cherry',3,6) ON DUPLICATE KEY UPDATE `user_id`=VALUES(`user_id`)

model是声明映射关系的对象类型，通过这个对象类型，找到表名和字段。

	var u Userdb.Debug().Take(&u, 3)var a Articledb.Debug().Take(&a, 5)db.Debug().Model(&u).Association("Articles").Append(&a)[1.409ms] [rows:1] SELECT * FROM `user` WHERE `user`.`id` = 3 LIMIT 1[1.254ms] [rows:1] SELECT * FROM `article` WHERE `article`.`id` = 5 LIMIT 1[2.285ms] [rows:2] INSERT INTO `article` (`title`,`user_id`,`id`) VALUES ('redis',3,5) ON DUPLICATE KEY UPDATE `user_id`=VALUES(`user_id`)