golang gorm增刪改查db.Model db.Where db.Table

1. 創建

創建記錄：

user := User{Name: "Jinzhu", Age: 18, Birthday: time.Now()}

db.NewRecord(user) // => 主鍵爲空返回`true`

db.Create(&user)

db.NewRecord(user) // => 創建`user`後返回`false`

設置默認值：
可以在gorm tag中定義默認值，然後插入SQL將忽略具有默認值的這些字段，並且其值爲空，並且在將記錄插入數據庫後，gorm將從數據庫加載這些字段的值。

type Animal struct {
    ID   int64
    Name string `gorm:"default:'galeone'"`
    Age  int64
}

var animal = Animal{Age: 99, Name: ""}
db.Create(&animal)

INSERT INTO animals("age") values('99');
SELECT name from animals WHERE ID=111; // 返回主鍵爲 111
animal.Name => 'galeone'

2. 查詢

獲取：第一條記錄/ 最後一條記錄/ 所有記錄

// 獲取第一條記錄，按主鍵排序
db.First(&user)
//// SELECT * FROM users ORDER BY id LIMIT 1;

// 獲取最後一條記錄，按主鍵排序
db.Last(&user)
//// SELECT * FROM users ORDER BY id DESC LIMIT 1;

// 獲取所有記錄
db.Find(&users)
//// SELECT * FROM users;

// 使用主鍵獲取記錄
db.First(&user, 10)
//// SELECT * FROM users WHERE id = 10;

Where查詢條件

// 獲取第一個匹配記錄
db.Where("name = ?", "jinzhu").First(&user)
//// SELECT * FROM users WHERE name = 'jinzhu' limit 1;

// 獲取所有匹配記錄
db.Where("name = ?", "jinzhu").Find(&users)
//// SELECT * FROM users WHERE name = 'jinzhu';
// IN
db.Where("name in (?)", []string{"jinzhu", "jinzhu 2"}).Find(&users)

// LIKE
db.Where("name LIKE ?", "%jin%").Find(&users)

// AND
db.Where("name = ? AND age >= ?", "jinzhu", "22").Find(&users)

注意：當使用struct查詢時，GORM將只查詢那些具有值的字段

// Struct
db.Where(&User{Name: "zhangyang", Age: 20}).First(&user)
//// SELECT * FROM users WHERE name = "zhangyang" AND age = 20 LIMIT 1;

// Map
db.Where(map[string]interface{}{"name": "zhangyang", "age": 20}).Find(&users)
//// SELECT * FROM users WHERE name = "zhangyang" AND age = 20;

// 主鍵的Slice
db.Where([]int64{20, 21, 22}).Find(&users)
//// SELECT * FROM users WHERE id IN (20, 21, 22);

Not條件查詢

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;

Or條件查詢

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';

Select 指定要從數據庫檢索的字段,默認情況下，將選擇所有字段;

db.Select("name, age").Find(&users)
//// SELECT name, age FROM users;

db.Select([]string{"name", "age"}).Find(&users)
//// SELECT name, age FROM users;

Order

db.Order("age desc, name").Find(&users)
//// SELECT * FROM users ORDER BY age desc, name;

// Multiple orders
db.Order("age desc").Order("name").Find(&users)
//// SELECT * FROM users ORDER BY age desc, name;

// ReOrder 從數據庫檢索記錄時指定順序，將重排序設置爲true以覆蓋定義的條件
db.Order("age desc").Find(&users1).Order("age", true).Find(&users2)
//// SELECT * FROM users ORDER BY age desc; (users1)
//// SELECT * FROM users ORDER BY age; (users2)

Limit , Offset
指定要檢索的記錄數

db.Limit(3).Find(&users)
//// SELECT * FROM users LIMIT 3;

指定在開始返回記錄之前要跳過的記錄數

db.Offset(3).Find(&users)
//// SELECT * FROM users OFFSET 3;

// Cancel offset condition with -1
db.Offset(10).Find(&users1).Offset(-1).Find(&users2)
//// SELECT * FROM users OFFSET 10; (users1)
//// SELECT * FROM users; (users2)

Count，Group & Having，Join
獲取記錄數

db.Where("name = ?", "jinzhu").Or("name = ?", "jinzhu 2").Find(&users).Count(&count)
//// SELECT * from USERS WHERE name = 'jinzhu' OR name = 'jinzhu 2'; (users)
//// SELECT count(*) FROM users WHERE name = 'jinzhu' OR name = 'jinzhu 2'; (count)

db.Model(&User{}).Where("name = ?", "jinzhu").Count(&count)
//// SELECT count(*) FROM users WHERE name = 'jinzhu'; (count)

//指定表deleted_users
db.Table("deleted_users").Count(&count)
//

rows, err := db.Table("orders").Select("date(created_at) as date, sum(amount) as total").Group("date(created_at)").Rows()

rows, err := db.Table("users").Select("users.name, emails.email").Joins("left join emails on emails.user_id = users.id").Rows()

3. 更新

更新全部字段
Save將包括執行更新SQL時的所有字段，即使它沒有更改

db.First(&user)

user.Name = "jinzhu 2"
user.Age = 100
db.Save(&user)

//// UPDATE users SET name='jinzhu 2', age=100, birthday='2016-01-01', updated_at = '2013-11-17 21:34:10' WHERE id=111;

更新指定字段
如果只想更新指定字段，可以使用Update, Updates

// 更新單個屬性（如果更改）
db.Model(&user).Update("name", "hello")
//// UPDATE users SET name='hello', updated_at='2013-11-17 21:34:10' WHERE id=111;

// 使用組合條件更新單個屬性
db.Model(&user).Where("active = ?", true).Update("name", "hello")
//// UPDATE users SET name='hello', updated_at='2013-11-17 21:34:10' WHERE id=111 AND active=true;

// 使用`map`更新多個屬性，只會更新這些更改的字段
db.Model(&user).Updates(map[string]interface{}{"name": "hello", "age": 18, "actived": false})
//// UPDATE users SET name='hello', age=18, actived=false, updated_at='2013-11-17 21:34:10' WHERE id=111;

// 使用`struct`更新多個屬性，只會更新這些更改的和非空白字段
db.Model(&user).Updates(User{Name: "hello", Age: 18})
//// UPDATE users SET name='hello', age=18, updated_at = '2013-11-17 21:34:10' WHERE id = 111;

// 警告:當使用struct更新時，FORM將僅更新具有非空值的字段
// 對於下面的更新，什麼都不會更新爲""，0，false是其類型的空白值
db.Model(&user).Updates(User{Name: "", Age: 0, Actived: false})

更新選擇的字段
如果您只想在更新時更新或忽略某些字段，可以使用Select, Omit

db.Model(&user).Select("name").Updates(map[string]interface{}{"name": "hello", "age": 18, "actived": 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, "actived": false})
//// UPDATE users SET age=18, actived=false, updated_at='2013-11-17 21:34:10' WHERE id=111;

4. 刪除

警告：刪除記錄時，需要確保其主要字段具有值，GORM將使用主鍵刪除記錄，如果主要字段爲空，GORM將刪除模型的所有記錄

// 刪除存在的記錄
db.Delete(&email)
//// DELETE from emails where id=10;

// 爲Delete語句添加額外的SQL選項
db.Set("gorm:delete_option", "OPTION (OPTIMIZE FOR UNKNOWN)").Delete(&email)
//// DELETE from emails where id=10 OPTION (OPTIMIZE FOR UNKNOWN);

批量刪除
刪除所有匹配記錄

db.Where("email LIKE ?", "%jinzhu%").Delete(Email{})
//// DELETE from emails where email LIKE "%jinhu%";

db.Delete(Email{}, "email LIKE ?", "%jinzhu%")
//// DELETE from emails where email LIKE "%jinhu%";