// ErrModelAccessibleFieldsRequired model accessible fields required
	ErrModelAccessibleFieldsRequired = errors.New("model accessible fields required")
	// ErrSubQueryRequired sub query required
	ErrSubQueryRequired = errors.New("sub query required")
	// ErrInvalidData unsupported data
	ErrInvalidData = errors.New("unsupported data")
	// ErrUnsupportedDriver unsupported driver
	ErrUnsupportedDriver = errors.New("unsupported driver")

			tx.Statement.AddClause(clause.Where{Exprs: exprs})
		}
	}
	tx.Statement.RaiseErrorOnNotFound = true
	tx.Statement.Dest = dest
	return tx.callbacks.Query().Execute(tx)
}

// Take finds the first record returned by the database in no specified order, matching given conditions conds
func (db *DB) Take(dest interface{}, conds ...interface{}) (tx *DB) {
	tx = db.Limit(1)

	Get() interface{}
	Put(interface{})
}

// CreateClausesInterface create clauses interface
type CreateClausesInterface interface {
	CreateClauses(*Field) []clause.Interface
}

// QueryClausesInterface query clauses interface
type QueryClausesInterface interface {
	QueryClauses(*Field) []clause.Interface
}

// UpdateClausesInterface update clauses interface
type UpdateClausesInterface interface {

}

// ViewOption view option
type ViewOption struct {
	Replace     bool   // If true, exec `CREATE`. If false, exec `CREATE OR REPLACE`
	CheckOption string // optional. e.g. `WITH [ CASCADED | LOCAL ] CHECK OPTION`
	Query       *DB    // required subquery.
}

// ColumnType column type interface
type ColumnType interface {
	Name() string
	DatabaseTypeName() string                 // varchar

		t.Fatalf("Failed to crate view, got %v", err)
	}

	var count int64
	if err := DB.Table("users_pets").Count(&count).Error; err != nil {
		t.Fatalf("should found created view")
	}

	if err := DB.Migrator().DropView("users_pets"); err != nil {
		t.Fatalf("Failed to drop view, got %v", err)
	}

	query = DB.Model(&User{}).Where("age > ?", 20)

	// 2. g2 select lock `conn.PrepareContext(ctx, query)`, now db.numOpen == db.maxOpen , wait for release.
	// 3. g1 tx exec insert, wait for unlock `conn.PrepareContext(ctx, query)` to finish tx and release.
	stmt, err := conn.PrepareContext(ctx, query)
	if err != nil {
		cacheStmt.prepareErr = err
		db.Mux.Lock()
		delete(db.Stmts, query)
		db.Mux.Unlock()
		return Stmt{}, err
	}

	db.Mux.Lock()

		var first, last User
		if err := DB.Where("id = ?", users[0].ID).First(&first).Error; err != nil {
			t.Errorf("errors happened when query before user: %v", err)
		}
		CheckUser(t, first, *users[0])

		if err := DB.Where("id = ?", users[2].ID).First(&last).Error; err != nil {
			t.Errorf("errors happened when query after user: %v", err)
		}
		CheckUser(t, last, *users[2])
	}

	if err := DB.Create(&users).Error; err != nil {

}

func doCheckPet(t *testing.T, pet Pet, expect Pet, unscoped bool) {
	if pet.ID != 0 {
		var newPet Pet
		if err := db(unscoped).Where("id = ?", pet.ID).First(&newPet).Error; err != nil {
			t.Fatalf("errors happened when query: %v", err)
		} else {
			AssertObjEqual(t, newPet, pet, "ID", "CreatedAt", "UpdatedAt", "DeletedAt", "UserID", "Name")
			AssertObjEqual(t, newPet, expect, "ID", "CreatedAt", "UpdatedAt", "DeletedAt", "UserID", "Name")
		}

	}

	var result ScannerValuerStruct

	if err := DB.Find(&result, "id = ?", data.ID).Error; err != nil {
		t.Fatalf("no error should happen when query scanner, valuer struct, but got %v", err)
	}

	if result.ExampleStructPtr.Val != "value2" {
		t.Errorf(`ExampleStructPtr.Val should equal to "value2", but got %v`, result.ExampleStructPtr.Val)
	}

		for k, v := range rm {
			resultsMap[k] = append(resultsMap[k], v...)
		}
		results = append(results, rs...)
	}
	return resultsMap, results
}

// ToQueryValues to query values
func ToQueryValues(table string, foreignKeys []string, foreignValues [][]interface{}) (interface{}, []interface{}) {
	queryValues := make([]interface{}, len(foreignValues))
	if len(foreignKeys) == 1 {