var duration time.Duration
	switch timePart {
	case timePartYear:
		return FromTimestamp(t.AddDate(int(qty), 0, 0)), nil
	case timePartMonth:
		return FromTimestamp(t.AddDate(0, int(qty), 0)), nil
	case timePartDay:
		return FromTimestamp(t.AddDate(0, 0, int(qty))), nil
	case timePartHour:
		duration = time.Duration(qty) * time.Hour
	case timePartMinute:

		return FromFloat(math.Pi)
	},
	func() *Value {
		return FromInt(0x1337)
	},
	func() *Value {
		t, err := time.Parse(time.RFC3339, "2006-01-02T15:04:05Z")
		if err != nil {
			panic(err)
		}
		return FromTimestamp(t)
	},
	func() *Value {
		return FromString("string contents")
	},
}

// altValueBuilders contains one constructor for each value type.

	if !ok {
		return nil, fmt.Errorf("%s() expects two timestamp arguments", sqlFnDateDiff)
	}

	return dateDiff(strings.ToUpper(d.DatePart), ts1, ts2)
}

func handleUTCNow() (*Value, error) {
	return FromTimestamp(time.Now().UTC()), nil
}

func handleSQLSubstring(r Record, e *SubstringFunc, tableAlias string) (val *Value, err error) {
	// Both forms `SUBSTRING('abc' FROM 2 FOR 1)` and
	// SUBSTRING('abc', 2, 1) are supported.

func FromString(str string) *Value {
	return &Value{value: str}
}

// FromBool creates a Value from a bool
func FromBool(b bool) *Value {
	return &Value{value: b}
}

// FromTimestamp creates a Value from a timestamp
func FromTimestamp(t time.Time) *Value {
	return &Value{value: t}
}

// FromNull creates a Value with Null value
func FromNull() *Value {
	return &Value{value: nil}
}