97 lines
2.3 KiB
Go
97 lines
2.3 KiB
Go
package main
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import (
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"fmt"
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"gorm.io/driver/sqlite"
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"gorm.io/gorm"
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)
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// 学生和课程：多对多关系
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type Student struct {
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ID uint `gorm:"primaryKey"`
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Name string `gorm:"size:100"`
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Courses []Course `gorm:"many2many:student_courses;"` // 多对多
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}
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type Course struct {
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ID uint `gorm:"primaryKey"`
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Name string `gorm:"size:100"`
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Students []Student `gorm:"many2many:student_courses;"` // 多对多
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}
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func main() {
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db, _ := gorm.Open(sqlite.Open("test.db"), &gorm.Config{})
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//db.AutoMigrate(&Student{}, &Course{})
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// 1. 创建课程
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//math := Course{Name: "Math"}
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//physics := Course{Name: "Physics"}
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//chemistry := Course{Name: "Chemistry"}
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//db.Create(&math)
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//db.Create(&physics)
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//db.Create(&chemistry)
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// 2. 创建学生并关联课程
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//alice := Student{
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// Name: "Alice",
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// Courses: []Course{math, physics},
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//}
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//bob := Student{
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// Name: "Bob",
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// Courses: []Course{physics, chemistry},
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//}
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//db.Create(&alice)
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//db.Create(&bob)
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//fmt.Println("Students and courses created")
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//查询数据库的alice的学生
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var alice Student
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db.Where("name = ?", "Alice").First(&alice)
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//查询数据库的Bob学生
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var bob Student
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db.Where("name = ?", "Bob").First(&bob)
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//查询课程
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var math Course
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db.Where("name = ?", "Math").First(&math)
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//// 5. 添加关联
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//db.Model(&alice).Association("Courses").Append(&chemistry)
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//fmt.Println("Alice enrolled in Chemistry")
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//// 7. 替换所有关联
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//db.Model(&alice).Association("Courses").Replace(&math)
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//fmt.Println("Alice now only takes Math")
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// 8. 清空关联
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db.Model(&bob).Association("Courses").Clear()
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fmt.Println("Bob dropped all courses")
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// 3. 查询学生的课程
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var student1 Student
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db.Preload("Courses").First(&student1, 1)
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fmt.Printf("%s's courses:\n", student1.Name)
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for _, course := range student1.Courses {
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fmt.Printf(" - %s\n", course.Name)
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}
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// 4. 查询课程的学生
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var course1 Course
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db.Preload("Students").First(&course1, 1)
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fmt.Printf("%s course students:\n", course1.Name)
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for _, student := range course1.Students {
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fmt.Printf(" - %s\n", student.Name)
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}
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//查询bob的课程
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var student2 Student
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db.Preload("Courses").First(&student2, 2)
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fmt.Printf("%s's courses:\n", student2.Name)
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for _, course := range student2.Courses {
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fmt.Printf(" - %s\n", course.Name)
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}
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}
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