创建
创建记录
user := User{Name: "Jinzhu", Age: 18, Birthday: time.Now()}
result := db.Create(&user) // 通过数据的指针来创建
user.ID // 返回插入数据的主键
result.Error // 返回 error
result.RowsAffected // 返回插入记录的条数
我们还可以使用 Create() 创建多项记录：
users := []*User{
User{Name: "Jinzhu", Age: 18, Birthday: time.Now()},
User{Name: "Jackson", Age: 19, Birthday: time.Now()},
}
result := db.Create(users) // pass a slice to insert multiple row
result.Error // returns error
result.RowsAffected // returns inserted records count
用指定的字段创建记录
创建记录并为指定的字段分配值：
db.Select("Name", "Age", "CreatedAt").Create(&user)
// INSERT INTO `users` (`name`,`age`,`created_at`) VALUES ("jinzhu", 18, "2020-07-04 11:05:21.775")
创建记录并忽略要省略的传递字段的值：
db.Omit("Name", "Age", "CreatedAt").Create(&user)
// INSERT INTO `users` (`birthday`,`updated_at`) VALUES ("2020-01-01 00:00:00.000", "2020-07-04 11:05:21.775")
批量插入
To efficiently insert large number of records, pass a slice to the Create method. GORM will generate a single SQL statement to insert all the data and backfill primary key values, hook methods will be invoked too. It will begin a transaction when records can be splited into multiple batches.
var users = []User{{Name: "jinzhu1"}, {Name: "jinzhu2"}, {Name: "jinzhu3"}}
db.Create(&users)
for _, user := range users {
user.ID // 1,2,3
}
You can specify batch size when creating with CreateInBatches, e.g:
var users = []User{{Name: "jinzhu_1"}, ...., {Name: "jinzhu_10000"}}
// batch size 100
db.CreateInBatches(users, 100)
Batch Insert is also supported when using Upsert and Create With Associations
NOTE initialize GORM with
CreateBatchSizeoption, allINSERTwill respect this option when creating record & associations
db, err := gorm.Open(sqlite.Open("gorm.db"), &gorm.Config{
CreateBatchSize: 1000,
})
db := db.Session(&gorm.Session{CreateBatchSize: 1000})
users = [5000]User{{Name: "jinzhu", Pets: []Pet{pet1, pet2, pet3}}...}
db.Create(&users)
// INSERT INTO users xxx (5 batches)
// INSERT INTO pets xxx (15 batches)
创建钩子
GORM allows user defined hooks to be implemented for BeforeSave, BeforeCreate, AfterSave, AfterCreate. These hook method will be called when creating a record, refer Hooks for details on the lifecycle
func (u *User) BeforeCreate(tx *gorm.DB) (err error) {
u.UUID = uuid.New()
if u.Role == "admin" {
return errors.New("invalid role")
}
return
}
If you want to skip Hooks methods, you can use the SkipHooks session mode, for example:
DB.Session(&gorm.Session{SkipHooks: true}).Create(&user)
DB.Session(&gorm.Session{SkipHooks: true}).Create(&users)
DB.Session(&gorm.Session{SkipHooks: true}).CreateInBatches(users, 100)
根据 Map 创建
GORM supports create from map[string]interface{} and []map[string]interface{}{}, e.g:
db.Model(&User{}).Create(map[string]interface{}{
"Name": "jinzhu", "Age": 18,
})
// batch insert from `[]map[string]interface{}{}`
db.Model(&User{}).Create([]map[string]interface{}{
{"Name": "jinzhu_1", "Age": 18},
{"Name": "jinzhu_2", "Age": 20},
})
NOTE When creating from map, hooks won’t be invoked, associations won’t be saved and primary key values won’t be back filled
使用 SQL 表达式、Context Valuer 创建记录
GORM allows insert data with SQL expression, there are two ways to achieve this goal, create from map[string]interface{} or Customized Data Types, for example:
// Create from map
db.Model(User{}).Create(map[string]interface{}{
"Name": "jinzhu",
"Location": clause.Expr{SQL: "ST_PointFromText(?)", Vars: []interface{}{"POINT(100 100)"}},
})
// INSERT INTO `users` (`name`,`location`) VALUES ("jinzhu",ST_PointFromText("POINT(100 100)"));
// Create from customized data type
type Location struct {
X, Y int
}
// Scan implements the sql.Scanner interface
func (loc *Location) Scan(v interface{}) error {
// Scan a value into struct from database driver
}
func (loc Location) GormDataType() string {
return "geometry"
}
func (loc Location) GormValue(ctx context.Context, db *gorm.DB) clause.Expr {
return clause.Expr{
SQL: "ST_PointFromText(?)",
Vars: []interface{}{fmt.Sprintf("POINT(%d %d)", loc.X, loc.Y)},
}
}
type User struct {
Name string
Location Location
}
db.Create(&User{
Name: "jinzhu",
Location: Location{X: 100, Y: 100},
})
// INSERT INTO `users` (`name`,`location`) VALUES ("jinzhu",ST_PointFromText("POINT(100 100)"))
高级选项
关联创建
When creating some data with associations, if its associations value is not zero-value, those associations will be upserted, and its Hooks methods will be invoked.
type CreditCard struct {
gorm.Model
Number string
UserID uint
}
type User struct {
gorm.Model
Name string
CreditCard CreditCard
}
db.Create(&User{
Name: "jinzhu",
CreditCard: CreditCard{Number: "411111111111"}
})
// INSERT INTO `users` ...
// INSERT INTO `credit_cards` ...
You can skip saving associations with Select, Omit, for example:
db.Omit("CreditCard").Create(&user)
// skip all associations
db.Omit(clause.Associations).Create(&user)
默认值
You can define default values for fields with tag default, for example:
type User struct {
ID int64
Name string `gorm:"default:galeone"`
Age int64 `gorm:"default:18"`
}
Then the default value will be used when inserting into the database for zero-value fields
NOTE Any zero value like
0,'',falsewon’t be saved into the database for those fields defined default value, you might want to use pointer type or Scanner/Valuer to avoid this, for example:
type User struct {
gorm.Model
Name string
Age *int `gorm:"default:18"`
Active sql.NullBool `gorm:"default:true"`
}
NOTE You have to setup the default tag for fields having default or virtual/generated value in database, if you want to skip a default value definition when migrating, you could use default:(-), for example:
type User struct {
ID string `gorm:"default:uuid_generate_v3()"` // db func
FirstName string
LastName string
Age uint8
FullName string `gorm:"->;type:GENERATED ALWAYS AS (concat(firstname,' ',lastname));default:(-);"`
}
When using virtual/generated value, you might need to disable its creating/updating permission, check out Field-Level Permission
Upsert 及冲突
GORM provides compatible Upsert support for different databases
import "gorm.io/gorm/clause"
// Do nothing on conflict
db.Clauses(clause.OnConflict{DoNothing: true}).Create(&user)
// Update columns to default value on `id` conflict
db.Clauses(clause.OnConflict{
Columns: []clause.Column{{Name: "id"}},
DoUpdates: clause.Assignments(map[string]interface{}{"role": "user"}),
}).Create(&users)
// MERGE INTO "users" USING *** WHEN NOT MATCHED THEN INSERT *** WHEN MATCHED THEN UPDATE SET ***; SQL Server
// INSERT INTO `users` *** ON DUPLICATE KEY UPDATE ***; MySQL
// Use SQL expression
db.Clauses(clause.OnConflict{
Columns: []clause.Column{{Name: "id"}},
DoUpdates: clause.Assignments(map[string]interface{}{"count": gorm.Expr("GREATEST(count, VALUES(count))")}),
}).Create(&users)
// INSERT INTO `users` *** ON DUPLICATE KEY UPDATE `count`=GREATEST(count, VALUES(count));
// Update columns to new value on `id` conflict
db.Clauses(clause.OnConflict{
Columns: []clause.Column{{Name: "id"}},
DoUpdates: clause.AssignmentColumns([]string{"name", "age"}),
}).Create(&users)
// MERGE INTO "users" USING *** WHEN NOT MATCHED THEN INSERT *** WHEN MATCHED THEN UPDATE SET "name"="excluded"."name"; SQL Server
// INSERT INTO "users" *** ON CONFLICT ("id") DO UPDATE SET "name"="excluded"."name", "age"="excluded"."age"; PostgreSQL
// INSERT INTO `users` *** ON DUPLICATE KEY UPDATE `name`=VALUES(name),`age`=VALUES(age); MySQL
// Update all columns to new value on conflict except primary keys and those columns having default values from sql func
db.Clauses(clause.OnConflict{
UpdateAll: true,
}).Create(&users)
// INSERT INTO "users" *** ON CONFLICT ("id") DO UPDATE SET "name"="excluded"."name", "age"="excluded"."age", ...;
// INSERT INTO `users` *** ON DUPLICATE KEY UPDATE `name`=VALUES(name),`age`=VALUES(age), ...; MySQL
Also checkout FirstOrInit, FirstOrCreate on Advanced Query
Checkout Raw SQL and SQL Builder for more details
