Create

Create Record

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

result := db.Create(&user) // pass pointer of data to Create

user.ID             // returns inserted data's primary key
result.Error        // returns error
result.RowsAffected // returns inserted records count

We can also create multiple records with Create():

users := []*User{
  {Name: "Jinzhu", Age: 18, Birthday: time.Now()},
  {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

NOTE You cannot pass a struct to ‘create’, so you should pass a pointer to the data.

Create Record With Selected Fields

Create a record and assign a value to the fields specified.

db.Select("Name", "Age", "CreatedAt").Create(&user)
// INSERT INTO `users` (`name`,`age`,`created_at`) VALUES ("jinzhu", 18, "2020-07-04 11:05:21.775")

Create a record and ignore the values for fields passed to omit.

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")

Batch Insert

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 split 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 CreateBatchSize option, all INSERT will 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)

Create Hooks

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)

Create From Map

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

Create From SQL Expression/Context Valuer

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)"))

Advanced

Create With Associations

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)

Default Values

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, '', false won’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:(-);"`
}

NOTE SQLite doesn’t support some records are default values when batch insert.
See SQLite Insert stmt. For example:

type Pet struct {
  Name string `gorm:"default:cat"`
}

// In SQLite, this is not supported, so GORM will build a wrong SQL to raise error:
// INSERT INTO `pets` (`name`) VALUES ("dog"),(DEFAULT) RETURNING `name`
db.Create(&[]Pet{{Name: "dog"}, {}})

A viable alternative is to assign default value to fields in the hook, e.g.

func (p *Pet) BeforeCreate(tx *gorm.DB) (err error) {
  if p.Name == "" {
    p.Name = "cat"
  }
}

You can see more info in issues#6335

When using virtual/generated value, you might need to disable its creating/updating permission, check out Field-Level Permission

Upsert / On Conflict

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