初始化Go学习项目

go-gorm-demo/crud_read.go

@@ -0,0 +1,72 @@
+package main
+
+import (
+	"fmt"
+
+	"gorm.io/driver/sqlite"
+	"gorm.io/gorm"
+)
+
+//type User struct {
+//	ID        uint   `gorm:"primaryKey"`
+//	Name      string `gorm:"size:100"`
+//	Email     string `gorm:"size:100;unique"`
+//	Age       int
+//	CreatedAt time.Time
+//}
+
+func main() {
+	db, _ := gorm.Open(sqlite.Open("test.db"), &gorm.Config{})
+
+	// 先插入测试数据
+	db.AutoMigrate(&User{})
+	db.Create(&User{Name: "Alice", Email: "alice@example.com", Age: 30})
+	db.Create(&User{Name: "Bob", Email: "bob@example.com", Age: 25})
+	db.Create(&User{Name: "Charlie", Email: "charlie@example.com", Age: 35})
+
+	// 1. 根据 ID 查询
+	var user User
+	db.First(&user, 1) // 查询 ID=1 的用户
+	fmt.Printf("User ID=1: %s (%s)\n", user.Name, user.Email)
+
+	// 2. 按条件查询单条
+	var user2 User
+	db.Where("email = ?", "bob@example.com").First(&user2)
+	fmt.Printf("User by email: %s (age=%d)\n", user2.Name, user2.Age)
+
+	// 3. 查询所有
+	var users []User
+	db.Find(&users)
+	fmt.Printf("Total users: %d\n", len(users))
+
+	// 4. 按条件查询多条
+	var adults []User
+	db.Where("age >= ?", 30).Find(&adults)
+	fmt.Printf("Users age >= 30: %d\n", len(adults))
+
+	// 5. 使用 IN 查询
+	var selectedUsers []User
+	db.Where("id IN ?", []int{1, 2}).Find(&selectedUsers)
+	fmt.Printf("Selected users: %d\n", len(selectedUsers))
+
+	// 6. 排序查询
+	var sortedUsers []User
+	db.Order("age DESC").Find(&sortedUsers)
+	fmt.Println("Users sorted by age (DESC):")
+	for _, u := range sortedUsers {
+		fmt.Printf("  - %s (age=%d)\n", u.Name, u.Age)
+	}
+
+	// 7. 分页查询
+	var pageUsers []User
+	db.Offset(0).Limit(2).Find(&pageUsers)
+	fmt.Printf("Page 1 (limit 2): %d users\n", len(pageUsers))
+
+	// 8. 组合查询
+	var combinedUsers []User
+	db.Where("age > ?", 25).
+		Order("age DESC").
+		Limit(2).
+		Find(&combinedUsers)
+	fmt.Printf("Combined query: %d users\n", len(combinedUsers))
+}