// First find first record that match given conditions, order by primary key
func (db *DB) First(dest interface{}, conds ...interface{}) (tx *DB) {
	tx = db.Limit(1).Order(clause.OrderByColumn{
		Column: clause.Column{Table: clause.CurrentTable, Name: clause.PrimaryKey},
	})
	if len(conds) > 0 {
		tx.Statement.AddClause(clause.Where{Exprs: tx.Statement.BuildCondition(conds[0], conds[1:]...)})
	}
	tx.Statement.RaiseErrorOnNotFound = true // 提升ErrorOnNotFound
	tx.Statement.Dest = dest
	tx.callbacks.Query().Execute(tx)
	return
}

// Take return a record that match given conditions, the order will depend on the database implementation
func (db *DB) Take(dest interface{}, conds ...interface{}) (tx *DB) {
	tx = db.Limit(1)
	if len(conds) > 0 {
		tx.Statement.AddClause(clause.Where{Exprs: tx.Statement.BuildCondition(conds[0], conds[1:]...)})
	}
	tx.Statement.RaiseErrorOnNotFound = true // 提升ErrorOnNotFound
	tx.Statement.Dest = dest
	tx.callbacks.Query().Execute(tx)
	return
}

// Last find last record that match given conditions, order by primary key
func (db *DB) Last(dest interface{}, conds ...interface{}) (tx *DB) {
	tx = db.Limit(1).Order(clause.OrderByColumn{
		Column: clause.Column{Table: clause.CurrentTable, Name: clause.PrimaryKey},
		Desc:   true,
	})
	if len(conds) > 0 {
		tx.Statement.AddClause(clause.Where{Exprs: tx.Statement.BuildCondition(conds[0], conds[1:]...)})
	}
	tx.Statement.RaiseErrorOnNotFound = true // 提升ErrorOnNotFound
	tx.Statement.Dest = dest
	tx.callbacks.Query().Execute(tx)
	return
}

// Find find records that match given conditions
func (db *DB) Find(dest interface{}, conds ...interface{}) (tx *DB) {
	tx = db.getInstance()
	if len(conds) > 0 {
		tx.Statement.AddClause(clause.Where{Exprs: tx.Statement.BuildCondition(conds[0], conds[1:]...)})
	}
    // 没有提升ErrorOnNotFound
	tx.Statement.Dest = dest
	tx.callbacks.Query().Execute(tx)
	return
}
-- gorm@v1.21.10/callbacks/callbacks.go:23
func RegisterDefaultCallbacks(db *gorm.DB, config *Config) {
	//...
	queryCallback := db.Callback().Query()
	queryCallback.Register("gorm:query", Query) // 注册Query处理器
	//...

-- gorm@v1.21.10/callbacks/query.go:13
func Query(db *gorm.DB) {
	if db.Error == nil {
		BuildQuerySQL(db)

		if !db.DryRun && db.Error == nil {
			rows, err := db.Statement.ConnPool.QueryContext(db.Statement.Context, db.Statement.SQL.String(), db.Statement.Vars...)
			if err != nil {
				db.AddError(err)
				return
			}
			defer rows.Close()

			gorm.Scan(rows, db, false) // 调用Scan
		}
	}
}

-- gorm@v1.21.10/scan.go:52
func Scan(rows *sql.Rows, db *DB, initialized bool) {
	columns, _ := rows.Columns()
	values := make([]interface{}, len(columns))
	db.RowsAffected = 0
    // ...
	if db.RowsAffected == 0 && db.Statement.RaiseErrorOnNotFound { // 这里,说明只有RaiseErrorOnNotFound=true,才会提升
		db.AddError(ErrRecordNotFound)
	}
}