diff --git a/internal/codec.go b/internal/codec.go
index 9c46060..4562d20 100644
--- a/internal/codec.go
+++ b/internal/codec.go
@@ -3,20 +3,21 @@ package internal
 type ValueType string
 
 const (
-	IntValueType       ValueType = "int64"
-	StringValueType    ValueType = "string"
-	BytesValueType     ValueType = "bytes"
-	FloatValueType     ValueType = "float"
-	NumericValueType   ValueType = "numeric"
-	BoolValueType      ValueType = "bool"
-	JsonValueType      ValueType = "json"
-	ArrayValueType     ValueType = "array"
-	StructValueType    ValueType = "struct"
-	DateValueType      ValueType = "date"
-	DatetimeValueType  ValueType = "datetime"
-	TimeValueType      ValueType = "time"
-	TimestampValueType ValueType = "timestamp"
-	IntervalValueType  ValueType = "interval"
+	IntValueType        ValueType = "int64"
+	StringValueType     ValueType = "string"
+	BytesValueType      ValueType = "bytes"
+	FloatValueType      ValueType = "float"
+	NumericValueType    ValueType = "numeric"
+	BigNumericValueType ValueType = "bignumeric"
+	BoolValueType       ValueType = "bool"
+	JsonValueType       ValueType = "json"
+	ArrayValueType      ValueType = "array"
+	StructValueType     ValueType = "struct"
+	DateValueType       ValueType = "date"
+	DatetimeValueType   ValueType = "datetime"
+	TimeValueType       ValueType = "time"
+	TimestampValueType  ValueType = "timestamp"
+	IntervalValueType   ValueType = "interval"
 )
 
 type ValueLayout struct {
diff --git a/internal/decoder.go b/internal/decoder.go
index 14e91f4..1495b8c 100644
--- a/internal/decoder.go
+++ b/internal/decoder.go
@@ -49,7 +49,11 @@ func decodeFromValueLayout(layout *ValueLayout) (Value, error) {
 	case NumericValueType:
 		r := new(big.Rat)
 		r.SetString(layout.Body)
-		return (*NumericValue)(r), nil
+		return &NumericValue{Rat: r}, nil
+	case BigNumericValueType:
+		r := new(big.Rat)
+		r.SetString(layout.Body)
+		return &NumericValue{Rat: r, isBigNumeric: true}, nil
 	case DateValueType:
 		t, err := parseDate(layout.Body)
 		if err != nil {
diff --git a/internal/encoder.go b/internal/encoder.go
index aac9eda..80fa46b 100644
--- a/internal/encoder.go
+++ b/internal/encoder.go
@@ -292,7 +292,10 @@ func numericValueFromLiteral(lit string) (*NumericValue, error) {
 	numericLit := matches[0][1]
 	r := new(big.Rat)
 	r.SetString(numericLit)
-	return (*NumericValue)(r), nil
+	if strings.Contains("BIGNUMERIC", lit) {
+		return &NumericValue{Rat: r, isBigNumeric: true}, nil
+	}
+	return &NumericValue{Rat: r}, nil
 }
 
 func jsonValueFromLiteral(lit string) (JsonValue, error) {
@@ -471,12 +474,18 @@ func CastValue(t types.Type, v Value) (Value, error) {
 			ret.m[key] = casted
 		}
 		return ret, nil
-	case types.NUMERIC, types.BIG_NUMERIC:
+	case types.NUMERIC:
 		r, err := v.ToRat()
 		if err != nil {
 			return nil, err
 		}
-		return (*NumericValue)(r), nil
+		return &NumericValue{Rat: r}, nil
+	case types.BIG_NUMERIC:
+		r, err := v.ToRat()
+		if err != nil {
+			return nil, err
+		}
+		return &NumericValue{Rat: r, isBigNumeric: true}, nil
 	case types.JSON:
 		j, err := v.ToJSON()
 		if err != nil {
@@ -591,10 +600,16 @@ func valueLayoutFromValue(v Value) (*ValueLayout, error) {
 			Body:   base64.StdEncoding.EncodeToString([]byte(vv)),
 		}, nil
 	case *NumericValue:
-		b, err := (*big.Rat)(vv).MarshalText()
+		b, err := vv.Rat.MarshalText()
 		if err != nil {
 			return nil, err
 		}
+		if vv.isBigNumeric {
+			return &ValueLayout{
+				Header: BigNumericValueType,
+				Body:   string(b),
+			}, nil
+		}
 		return &ValueLayout{
 			Header: NumericValueType,
 			Body:   string(b),
diff --git a/internal/function_bind.go b/internal/function_bind.go
index fdaf3a2..3417407 100644
--- a/internal/function_bind.go
+++ b/internal/function_bind.go
@@ -584,7 +584,7 @@ func bindParseBigNumeric(args ...Value) (Value, error) {
 	if err != nil {
 		return nil, err
 	}
-	return PARSE_NUMERIC(numeric)
+	return PARSE_BIGNUMERIC(numeric)
 }
 
 func bindFarmFingerprint(args ...Value) (Value, error) {
diff --git a/internal/function_numeric.go b/internal/function_numeric.go
index f14be0f..cc73315 100644
--- a/internal/function_numeric.go
+++ b/internal/function_numeric.go
@@ -10,5 +10,13 @@ func PARSE_NUMERIC(numeric string) (Value, error) {
 	if _, ok := r.SetString(numeric); !ok {
 		return nil, fmt.Errorf("unexpected numeric literal: %s", numeric)
 	}
-	return (*NumericValue)(r), nil
+	return &NumericValue{Rat: r}, nil
+}
+
+func PARSE_BIGNUMERIC(numeric string) (Value, error) {
+	r := new(big.Rat)
+	if _, ok := r.SetString(numeric); !ok {
+		return nil, fmt.Errorf("unexpected numeric literal: %s", numeric)
+	}
+	return &NumericValue{Rat: r, isBigNumeric: true}, nil
 }
diff --git a/internal/rows.go b/internal/rows.go
index 73cf3db..1e25b37 100644
--- a/internal/rows.go
+++ b/internal/rows.go
@@ -5,9 +5,7 @@ import (
 	"database/sql/driver"
 	"fmt"
 	"io"
-	"math/big"
 	"reflect"
-	"strings"
 	"time"
 
 	"github.com/goccy/go-json"
@@ -221,27 +219,13 @@ func (r *Rows) assignInterfaceValue(src Value, dst reflect.Value, typ *Type) err
 		if err != nil {
 			return err
 		}
-		r := new(big.Rat)
-		if _, ok := r.SetString(s); !ok {
-			return fmt.Errorf("unexpected numeric value: %s", s)
-		}
-		f := r.FloatString(9)
-		f = strings.TrimRight(f, "0")
-		f = strings.TrimRight(f, ".")
-		dst.Set(reflect.ValueOf(f))
+		dst.Set(reflect.ValueOf(s))
 	case types.BIG_NUMERIC:
 		s, err := src.ToString()
 		if err != nil {
 			return err
 		}
-		r := new(big.Rat)
-		if _, ok := r.SetString(s); !ok {
-			return fmt.Errorf("unexpected bignumeric value: %s", s)
-		}
-		f := r.FloatString(38)
-		f = strings.TrimRight(f, "0")
-		f = strings.TrimRight(f, ".")
-		dst.Set(reflect.ValueOf(f))
+		dst.Set(reflect.ValueOf(s))
 	case types.DATE:
 		date, err := src.ToJSON()
 		if err != nil {
diff --git a/internal/value.go b/internal/value.go
index 1b5220e..6104a88 100644
--- a/internal/value.go
+++ b/internal/value.go
@@ -587,37 +587,43 @@ func (fv FloatValue) Interface() interface{} {
 	return float64(fv)
 }
 
-type NumericValue big.Rat
+type NumericValue struct {
+	*big.Rat
+	isBigNumeric bool
+}
 
 func (nv *NumericValue) Add(v Value) (Value, error) {
 	z := new(big.Rat)
-	x := (*big.Rat)(nv)
+	x := nv.Rat
 	y, err := v.ToRat()
 	if err != nil {
 		return nil, err
 	}
-	return (*NumericValue)(z.Add(x, y)), nil
+	nv.Rat = z.Add(x, y)
+	return nv, nil
 }
 
 func (nv *NumericValue) Sub(v Value) (Value, error) {
 	z := new(big.Rat)
-	x := (*big.Rat)(nv)
+	x := nv.Rat
 	y, err := v.ToRat()
 	if err != nil {
 		return nil, err
 	}
 	zy := new(big.Rat)
-	return (*NumericValue)(z.Add(x, zy.Neg(y))), nil
+	nv.Rat = z.Add(x, zy.Neg(y))
+	return nv, nil
 }
 
 func (nv *NumericValue) Mul(v Value) (Value, error) {
 	z := new(big.Rat)
-	x := (*big.Rat)(nv)
+	x := nv.Rat
 	y, err := v.ToRat()
 	if err != nil {
 		return nil, err
 	}
-	return (*NumericValue)(z.Mul(x, y)), nil
+	nv.Rat = z.Mul(x, y)
+	return nv, nil
 }
 
 func (nv *NumericValue) Div(v Value) (ret Value, e error) {
@@ -627,17 +633,18 @@ func (nv *NumericValue) Div(v Value) (ret Value, e error) {
 		}
 	}()
 	z := new(big.Rat)
-	x := (*big.Rat)(nv)
+	x := nv.Rat
 	y, err := v.ToRat()
 	if err != nil {
 		return nil, err
 	}
 	zy := new(big.Rat)
-	return (*NumericValue)(z.Mul(x, zy.Inv(y))), nil
+	nv.Rat = z.Mul(x, zy.Inv(y))
+	return nv, nil
 }
 
 func (nv *NumericValue) EQ(v Value) (bool, error) {
-	x := (*big.Rat)(nv)
+	x := nv.Rat
 	y, err := v.ToRat()
 	if err != nil {
 		return false, err
@@ -646,7 +653,7 @@ func (nv *NumericValue) EQ(v Value) (bool, error) {
 }
 
 func (nv *NumericValue) GT(v Value) (bool, error) {
-	x := (*big.Rat)(nv)
+	x := nv.Rat
 	y, err := v.ToRat()
 	if err != nil {
 		return false, err
@@ -655,7 +662,7 @@ func (nv *NumericValue) GT(v Value) (bool, error) {
 }
 
 func (nv *NumericValue) GTE(v Value) (bool, error) {
-	x := (*big.Rat)(nv)
+	x := nv.Rat
 	y, err := v.ToRat()
 	if err != nil {
 		return false, err
@@ -664,7 +671,7 @@ func (nv *NumericValue) GTE(v Value) (bool, error) {
 }
 
 func (nv *NumericValue) LT(v Value) (bool, error) {
-	x := (*big.Rat)(nv)
+	x := nv.Rat
 	y, err := v.ToRat()
 	if err != nil {
 		return false, err
@@ -673,7 +680,7 @@ func (nv *NumericValue) LT(v Value) (bool, error) {
 }
 
 func (nv *NumericValue) LTE(v Value) (bool, error) {
-	x := (*big.Rat)(nv)
+	x := nv.Rat
 	y, err := v.ToRat()
 	if err != nil {
 		return false, err
@@ -682,24 +689,36 @@ func (nv *NumericValue) LTE(v Value) (bool, error) {
 }
 
 func (nv *NumericValue) ToInt64() (int64, error) {
-	return (*big.Rat)(nv).Num().Int64(), nil
+	return nv.Rat.Num().Int64(), nil
+}
+
+func (nv *NumericValue) toString() string {
+	var v string
+	if nv.isBigNumeric {
+		v = nv.Rat.FloatString(38)
+	} else {
+		v = nv.Rat.FloatString(9)
+	}
+	v = strings.TrimRight(v, "0")
+	v = strings.TrimRight(v, ".")
+	return v
 }
 
 func (nv *NumericValue) ToString() (string, error) {
-	return (*big.Rat)(nv).RatString(), nil
+	return nv.toString(), nil
 }
 
 func (nv *NumericValue) ToBytes() ([]byte, error) {
-	return []byte((*big.Rat)(nv).RatString()), nil
+	return []byte(nv.toString()), nil
 }
 
 func (nv *NumericValue) ToFloat64() (float64, error) {
-	f, _ := (*big.Rat)(nv).Float64()
+	f, _ := nv.Rat.Float64()
 	return f, nil
 }
 
 func (nv *NumericValue) ToBool() (bool, error) {
-	v := (*big.Rat)(nv).Num().Int64()
+	v := nv.Rat.Num().Int64()
 	if v == 1 {
 		return true, nil
 	} else if v == 0 {
@@ -717,7 +736,7 @@ func (nv *NumericValue) ToStruct() (*StructValue, error) {
 }
 
 func (nv *NumericValue) ToJSON() (string, error) {
-	return (*big.Rat)(nv).RatString(), nil
+	return nv.toString(), nil
 }
 
 func (nv *NumericValue) ToTime() (time.Time, error) {
@@ -725,15 +744,15 @@ func (nv *NumericValue) ToTime() (time.Time, error) {
 }
 
 func (nv *NumericValue) ToRat() (*big.Rat, error) {
-	return (*big.Rat)(nv), nil
+	return nv.Rat, nil
 }
 
 func (nv *NumericValue) Format(verb rune) string {
-	return (*big.Rat)(nv).RatString()
+	return nv.toString()
 }
 
 func (nv *NumericValue) Interface() interface{} {
-	f, _ := (*big.Rat)(nv).Float64()
+	f, _ := nv.Rat.Float64()
 	return f
 }
 
diff --git a/query_test.go b/query_test.go
index 6679e29..daff25d 100644
--- a/query_test.go
+++ b/query_test.go
@@ -3087,6 +3087,11 @@ SELECT
 			query:        `SELECT PARSE_BIGNUMERIC("123.45"), PARSE_BIGNUMERIC("123.456E37"), PARSE_BIGNUMERIC("1.123456789012345678901234567890123456789")`,
 			expectedRows: [][]interface{}{{"123.45", "1234560000000000000000000000000000000000", "1.12345678901234567890123456789012345679"}},
 		},
+		{
+			name:         "cast numeric and bignumeric to string",
+			query:        `SELECT cast(PARSE_NUMERIC("123.456") as STRING), cast(PARSE_BIGNUMERIC("123.456") as STRING)`,
+			expectedRows: [][]interface{}{{"123.456", "123.456"}},
+		},
 
 		// uuid functions
 		{