Gorm single table operation insert data

Create table AutoMigrate, and insert data db.Create  

package main

import (
	"fmt"
	"gorm.io/driver/mysql"
	"gorm.io/gorm"
)

type Student struct {
	ID     uint   `gorm:"size:3"`
	Name   string `gorm:"size:3"`
	Age    int    `gorm:"size:3"`
	Gender bool
	Email  *string `gorm:"size:32"`
}

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.AutoMigrate(&Student{})

	email := "[email protected]"
	//添加记录，实例化结构体
	s1 := &Student{
		Name:   "lu",
		Age:    21,
		Gender: true,
		Email:  &email,
	}
	err := db.Debug().Create(s1).Error
	fmt.Println(err)

}

[4.019ms] [rows:1] INSERT INTO `students` (`name`,`age`,`gender`,`email`) VALUES ('lu',21,true,'[email protected]')
<nil>

If you comment out name and email, you can see that the string type is an empty string, and the other *string type is null. So the value of email can be Email: nil

	//email := "[email protected]"
	//添加记录，实例化结构体
	s1 := &Student{
		//Name:   "lu",
		Age:    21,
		Gender: true,
		//Email:  &email,
	}


[3.829ms] [rows:1] INSERT INTO `students` (`name`,`age`,`gender`,`email`) VALUES ('',21,true,NULL)

mysql> select * from students;
+----+------+------+--------+------------+
| id | name | age  | gender | email      |
+----+------+------+--------+------------+
|  1 | lu   |   21 |      1 | [email protected] |
|  2 |      |   21 |      1 | NULL       |
+----+------+------+--------+------------+

Although the ID value is not inserted into the structure, this value will be generated in the structure.

	s1 := &Student{
		//Name:   "lu",
		Age:    21,
		Gender: true,
		Email:  nil,
	}
	err := db.Debug().Create(s1).Error
	fmt.Printf("%#v \n", s1)

[3.833ms] [rows:1] INSERT INTO `students` (`name`,`age`,`gender`,`email`) VALUES ('',21,true,NULL)
&main.Student{ID:0x5, Name:"", Age:21, Gender:true, Email:(*string)(nil)} 

There are two places to pay attention to:

1. The pointer type is to better store NULL types, but when passing values, remember to pass pointers

2.Create accepts a pointer, not a value

Since what we pass is a pointer, after calling Create, the student object will have the record information on it, such as the created id

Batch insertion: slices or arrays need to be prepared, here create needs to pass in slice pointers

package main

import (
	"fmt"
	"gorm.io/driver/mysql"
	"gorm.io/gorm"
)

type Student struct {
	ID     uint   `gorm:"size:3"`
	Name   string `gorm:"size:3"`
	Age    int    `gorm:"size:3"`
	Gender bool
	Email  *string `gorm:"size:32"`
}

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.AutoMigrate(&Student{})
	
	var studentList []Student
	for i := 0; i < 10; i++ {
		studentList := append(studentList, Student{
			Name:   fmt.Sprintf("f%d", i),
			Age:    21 + i,
			Gender: true,
			Email:  nil,
		})
		db.Create(&studentList)
	}

	slist := []Student{
		{Name: "cc", Age: 23, Gender: true, Email: nil},
		{Name: "xx", Age: 24, Gender: false, Email: nil},
	}
	db.Create(&slist)
}