diff --git a/pkg/sql/codegen/attribute/checker.go b/pkg/sql/codegen/attribute/checker.go
new file mode 100644
index 0000000000..fa73853b0c
--- /dev/null
+++ b/pkg/sql/codegen/attribute/checker.go
@@ -0,0 +1,101 @@
+// Copyright 2019 The SQLFlow Authors. All rights reserved.
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package attribute
+
+import (
+	"fmt"
+)
+
+func newFloat32(f float32) *float32 {
+	return &f
+}
+
+// Float32RangeChecker is a helper function to generate range checkers on attribute.
+// lower/upper indicates the lower bound and upper bound of the attribute value.
+// If lower/upper is nil, it means no boundary.
+// includeLower/includeUpper indicates the inclusion of the bound.
+func Float32RangeChecker(lower, upper *float32, includeLower, includeUpper bool) func(interface{}) error {
+
+	checker := func(e interface{}) error {
+		f, ok := e.(float32)
+		if !ok {
+			return fmt.Errorf("expected type float32, received %T", e)
+		}
+
+		// NOTE(tony): nil means no boundary
+		if lower != nil {
+			if includeLower && !(*lower <= f) {
+				return fmt.Errorf("range check %v <= %v failed", *lower, f)
+			}
+			if !includeLower && !(*lower < f) {
+				return fmt.Errorf("range check %v < %v failed", *lower, f)
+			}
+		}
+
+		// NOTE(tony): nil means no boundary
+		if upper != nil {
+			if includeUpper && !(f <= *upper) {
+				return fmt.Errorf("range check %v <= %v failed", f, *upper)
+			}
+			if !includeUpper && !(f < *upper) {
+				return fmt.Errorf("range check %v < %v failed", f, *upper)
+			}
+		}
+
+		return nil
+	}
+
+	return checker
+}
+
+func newInt(i int) *int {
+	return &i
+}
+
+// IntRangeChecker is a helper function to generate range checkers on attribute.
+// lower/upper indicates the lower bound and upper bound of the attribute value.
+// If lower/upper is nil, it means no boundary.
+// includeLower/includeUpper indicates the inclusion of the bound.
+func IntRangeChecker(lower, upper *int, includeLower, includeUpper bool) func(interface{}) error {
+	checker := func(e interface{}) error {
+		i, ok := e.(int)
+		if !ok {
+			return fmt.Errorf("expected type float32, received %T", e)
+		}
+
+		// NOTE(tony): nil means no boundary
+		if lower != nil {
+			if includeLower && !(*lower <= i) {
+				return fmt.Errorf("range check %v <= %v failed", *lower, i)
+			}
+			if !includeLower && !(*lower < i) {
+				return fmt.Errorf("range check %v < %v failed", *lower, i)
+			}
+		}
+
+		// NOTE(tony): nil means no boundary
+		if upper != nil {
+			if includeUpper && !(i <= *upper) {
+				return fmt.Errorf("range check %v <= %v failed", i, *upper)
+			}
+			if !includeUpper && !(i < *upper) {
+				return fmt.Errorf("range check %v < %v failed", i, *upper)
+			}
+		}
+
+		return nil
+	}
+
+	return checker
+}
diff --git a/pkg/sql/codegen/attribute/checker_test.go b/pkg/sql/codegen/attribute/checker_test.go
new file mode 100644
index 0000000000..12f2e481c0
--- /dev/null
+++ b/pkg/sql/codegen/attribute/checker_test.go
@@ -0,0 +1,55 @@
+// Copyright 2019 The SQLFlow Authors. All rights reserved.
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package attribute
+
+import (
+	"github.com/stretchr/testify/assert"
+	"testing"
+)
+
+func TestFloat32RangeChecker(t *testing.T) {
+	a := assert.New(t)
+
+	checker := Float32RangeChecker(newFloat32(0.0), newFloat32(1.0), true, true)
+	a.Error(checker(float32(-1)))
+	a.NoError(checker(float32(0)))
+	a.NoError(checker(float32(0.5)))
+	a.NoError(checker(float32(1)))
+	a.Error(checker(float32(2)))
+
+	checker2 := Float32RangeChecker(newFloat32(0.0), newFloat32(1.0), false, false)
+	a.Error(checker2(float32(-1)))
+	a.Error(checker2(float32(0)))
+	a.NoError(checker2(float32(0.5)))
+	a.Error(checker2(float32(1)))
+	a.Error(checker2(float32(2)))
+}
+
+func TestIntRangeChecker(t *testing.T) {
+	a := assert.New(t)
+
+	checker := IntRangeChecker(newInt(0), newInt(2), true, true)
+	a.Error(checker(int(-1)))
+	a.NoError(checker(int(0)))
+	a.NoError(checker(int(1)))
+	a.NoError(checker(int(2)))
+	a.Error(checker(int(3)))
+
+	checker2 := IntRangeChecker(newInt(0), newInt(2), false, false)
+	a.Error(checker2(int(-1)))
+	a.Error(checker2(int(0)))
+	a.NoError(checker2(int(1)))
+	a.Error(checker2(int(2)))
+	a.Error(checker2(int(3)))
+}
diff --git a/pkg/sql/ir_generator.go b/pkg/sql/ir_generator.go
index 210affeb2d..52b8c1b243 100644
--- a/pkg/sql/ir_generator.go
+++ b/pkg/sql/ir_generator.go
@@ -146,8 +146,7 @@ func inferStringValue(expr string) interface{} {
 		return ret
 	}
 	if retFloat, err := strconv.ParseFloat(expr, 32); err == nil {
-		// always use float32 for attributes, we may never use a float64
-		// value as some attribute.
+		// Note(typhoonzero): always use float32 for attributes, we may never use a float64.
 		return float32(retFloat)
 	}
 	retString := strings.Trim(expr, "\"")