这是我参与「第五届青训营」伴学笔记创作活动的第 20 天
增
创建记录
type User struct {
ID int64
Name string
Age int64
}
默认值
type User struct {
ID int64
Name string `gorm:"default:'小王子'"`
Age int64
}
注意：在插入的时候，gorm会自动过滤空值，不进行插入。
例如：
var user = User{Name: "", Age: 99}
db.Create(&user)
等价于
INSERT INTO users("age") values('99')
批量添加
var users = []User{{Name: "jinzhu1"}, {Name: "jinzhu2"}, {Name: "jinzhu3"}}
DB.Create(&users)
for _, user := range users {
user.ID // 1,2,3
}
查
简单查询
gorm 提供了很多查询方法
// 根据主键查询第一条记录
db.First(&user)
//// SELECT * FROM users ORDER BY id LIMIT 1;
// 随机获取一条记录
db.Take(&user)
//// SELECT * FROM users LIMIT 1;
// 根据主键查询最后一条记录
db.Last(&user)
//// SELECT * FROM users ORDER BY id DESC LIMIT 1;
// 查询所有的记录
db.Find(&user)
//// SELECT * FROM users;
// 查询指定的某条记录(仅当主键为整型时可用)
db.First(&user, 10)
//// SELECT * FROM users WHERE id = 10;
条件查询
where
// Get first matched record
db.Where("name = ?", "jinzhu").First(&user)
//// SELECT * FROM users WHERE name = 'jinzhu' limit 1;
// Get all matched records
db.Where("name = ?", "jinzhu").Find(&users)
//// SELECT * FROM users WHERE name = 'jinzhu';
// <>
db.Where("name <> ?", "jinzhu").Find(&users)
//// SELECT * FROM users WHERE name <> 'jinzhu';
// IN
db.Where("name IN (?)", []string{"jinzhu", "jinzhu 2"}).Find(&users)
//// SELECT * FROM users WHERE name in ('jinzhu','jinzhu 2');
// LIKE
db.Where("name LIKE ?", "%jin%").Find(&users)
//// SELECT * FROM users WHERE name LIKE '%jin%';
// AND
db.Where("name = ? AND age >= ?", "jinzhu", "22").Find(&users)
//// SELECT * FROM users WHERE name = 'jinzhu' AND age >= 22;
// Time
db.Where("updated_at > ?", lastWeek).Find(&users)
//// SELECT * FROM users WHERE updated_at > '2000-01-01 00:00:00';
// BETWEEN
db.Where("created_at BETWEEN ? AND ?", lastWeek, today).Find(&users)
//// SELECT * FROM users WHERE created_at BETWEEN '2000-01-01 00:00:00' AND '2000-01-08 00:00:00';
NOT
db.Not("name", "jinzhu").First(&user)
//// SELECT * FROM users WHERE name <> "jinzhu" LIMIT 1;
// Not In
db.Not("name", []string{"jinzhu", "jinzhu 2"}).Find(&users)
//// SELECT * FROM users WHERE name NOT IN ("jinzhu", "jinzhu 2");
// Not In slice of primary keys
db.Not([]int64{1,2,3}).First(&user)
//// SELECT * FROM users WHERE id NOT IN (1,2,3);
db.Not([]int64{}).First(&user)
//// SELECT * FROM users;
// Plain SQL
db.Not("name = ?", "jinzhu").First(&user)
//// SELECT * FROM users WHERE NOT(name = "jinzhu");
// Struct
db.Not(User{Name: "jinzhu"}).First(&user)
//// SELECT * FROM users WHERE name <> "jinzhu";
Or
db.Where("role = ?", "admin").Or("role = ?", "super_admin").Find(&users)
//// SELECT * FROM users WHERE role = 'admin' OR role = 'super_admin';
// Struct
db.Where("name = 'jinzhu'").Or(User{Name: "jinzhu 2"}).Find(&users)
//// SELECT * FROM users WHERE name = 'jinzhu' OR name = 'jinzhu 2';
// Map
db.Where("name = 'jinzhu'").Or(map[string]interface{}{"name": "jinzhu 2"}).Find(&users)
//// SELECT * FROM users WHERE name = 'jinzhu' OR name = 'jinzhu 2';
高级查询
Order
db.Order("age desc, name").Find(&users)
// SELECT * FROM users ORDER BY age desc, name;
Limit
db.Limit(3).Find(&users)
//// SELECT * FROM users LIMIT 3;
// -1 取消 Limit 条件
db.Limit(10).Find(&users1).Limit(-1).Find(&users2)
//// SELECT * FROM users LIMIT 10; (users1)
//// SELECT * FROM users; (users2)
偏移
db.Limit(3).Find(&users)
//// SELECT * FROM users LIMIT 3;
// -1 取消 Limit 条件
db.Limit(10).Find(&users1).Limit(-1).Find(&users2)
//// SELECT * FROM users LIMIT 10; (users1)
//// SELECT * FROM users; (users2)
查询方法还有很多，自行查看官方文档
改
Save 更新所有字段
db.First(&user)
user.Name = "七米"
user.Age = 99
db.Save(&user)
会将 Model中的字段也更新
更新指定字段
Update 或 Updates
db.Model(&user).Update("name", "hello")
// 使用 struct 更新多个属性，只会更新其中有变化且为非零值的字段
db.Model(&user).Updates(User{Name: "hello", Age: 18})
忽略字段
- Select 只更新所选字段，忽略其他字段
- Omit 忽略所选字段，更新其他字段
db.Model(&user).Select("name").Updates(map[string]interface{}{"name": "hello", "age": 18, "active": false})
//// UPDATE users SET name='hello', updated_at='2013-11-17 21:34:10' WHERE id=111;
db.Model(&user).Omit("name").Updates(map[string]interface{}{"name": "hello", "age": 18, "active": false})
//// UPDATE users SET age=18, active=false, updated_at='2013-11-17 21:34:10' WHERE id=111;
删除
// 删除现有记录
db.Delete(&email)
批量删除
db.Where("email LIKE ?", "%jinzhu%").Delete(Email{})
//// DELETE from emails where email LIKE "%jinzhu%";
软删除
如果一个 model 有 DeletedAt 字段，他将自动获得软删除的功能！ 当调用 Delete 方法时， 记录不会真正的从数据库中被删除， 只会将DeletedAt 字段的值会被设置为当前时间
物理删除
// Unscoped 方法可以物理删除记录
db.Unscoped().Delete(&order)
//// DELETE FROM orders WHERE id=10;
``
## 参考
1. [GORM CRUD指南 | 李文周的博客 (liwenzhou.com)](https://www.liwenzhou.com/posts/Go/gorm-crud/)
2. [创建 | GORM - The fantastic ORM library for Golang, aims to be developer friendly.](https://gorm.cn/zh_CN/docs/create.html)
3.
