diff --git a/internal/function_aggregate.go b/internal/function_aggregate.go
index 8095999..a983741 100644
--- a/internal/function_aggregate.go
+++ b/internal/function_aggregate.go
@@ -81,32 +81,20 @@ func (f *ARRAY_AGG) Step(v Value, opt *AggregatorOption) error {
 
 func (f *ARRAY_AGG) Done() (Value, error) {
 	if f.opt != nil && len(f.opt.OrderBy) != 0 {
-		for orderBy := 0; orderBy < len(f.opt.OrderBy); orderBy++ {
-			if f.opt.OrderBy[orderBy].IsAsc {
-				sort.Slice(f.values, func(i, j int) bool {
-					if f.values[i].OrderBy[orderBy].Value == nil {
-						return true
-					}
-					
-					if f.values[j].OrderBy[orderBy].Value == nil {
-						return false
-					}
-					v, _ := f.values[i].OrderBy[orderBy].Value.LT(f.values[j].OrderBy[orderBy].Value)
-					return v
-				})
-			} else {
-				sort.Slice(f.values, func(i, j int) bool {
-					if f.values[i].OrderBy[orderBy].Value == nil {
-						return true
-					}
-					if f.values[j].OrderBy[orderBy].Value == nil {
-						return false
-					}
-					v, _ := f.values[i].OrderBy[orderBy].Value.GT(f.values[j].OrderBy[orderBy].Value)
-					return v
-				})
+		sort.Slice(f.values, func(i, j int) bool {
+			for orderBy := 0; orderBy < len(f.opt.OrderBy); orderBy++ {
+				isAsc := f.opt.OrderBy[orderBy].IsAsc
+				result, areEqual, _ := shouldComeBefore(
+					f.values[i].OrderBy[orderBy].Value,
+					f.values[j].OrderBy[orderBy].Value,
+					isAsc,
+				)
+				if !areEqual {
+					return result
+				}
 			}
-		}
+			return false
+		})
 	}
 	if f.opt != nil && f.opt.Limit != nil {
 		minLen := int64(len(f.values))
@@ -146,31 +134,20 @@ func (f *ARRAY_CONCAT_AGG) Step(v *ArrayValue, opt *AggregatorOption) error {
 
 func (f *ARRAY_CONCAT_AGG) Done() (Value, error) {
 	if f.opt != nil && len(f.opt.OrderBy) != 0 {
-		for orderBy := 0; orderBy < len(f.opt.OrderBy); orderBy++ {
-			if f.opt.OrderBy[orderBy].IsAsc {
-				sort.Slice(f.values, func(i, j int) bool {
-					if f.values[i].OrderBy[orderBy].Value == nil {
-						return true
-					}
-					if f.values[j].OrderBy[orderBy].Value == nil {
-						return false
-					}
-					v, _ := f.values[i].OrderBy[orderBy].Value.LT(f.values[j].OrderBy[orderBy].Value)
-					return v
-				})
-			} else {
-				sort.Slice(f.values, func(i, j int) bool {
-					if f.values[i].OrderBy[orderBy].Value == nil {
-						return true
-					}
-					if f.values[j].OrderBy[orderBy].Value == nil {
-						return false
-					}
-					v, _ := f.values[i].OrderBy[orderBy].Value.GT(f.values[j].OrderBy[orderBy].Value)
-					return v
-				})
+		sort.Slice(f.values, func(i, j int) bool {
+			for orderBy := 0; orderBy < len(f.opt.OrderBy); orderBy++ {
+				isAsc := f.opt.OrderBy[orderBy].IsAsc
+				result, areEqual, _ := shouldComeBefore(
+					f.values[i].OrderBy[orderBy].Value,
+					f.values[j].OrderBy[orderBy].Value,
+					isAsc,
+				)
+				if !areEqual {
+					return result
+				}
 			}
-		}
+			return false
+		})
 	}
 	if f.opt != nil && f.opt.Limit != nil {
 		minLen := int64(len(f.values))
@@ -491,19 +468,20 @@ func (f *STRING_AGG) Step(v Value, delim string, opt *AggregatorOption) error {
 
 func (f *STRING_AGG) Done() (Value, error) {
 	if f.opt != nil && len(f.opt.OrderBy) != 0 {
-		for orderBy := 0; orderBy < len(f.opt.OrderBy); orderBy++ {
-			if f.opt.OrderBy[orderBy].IsAsc {
-				sort.Slice(f.values, func(i, j int) bool {
-					v, _ := f.values[i].OrderBy[orderBy].Value.LT(f.values[j].OrderBy[orderBy].Value)
-					return v
-				})
-			} else {
-				sort.Slice(f.values, func(i, j int) bool {
-					v, _ := f.values[i].OrderBy[orderBy].Value.GT(f.values[j].OrderBy[orderBy].Value)
-					return v
-				})
+		sort.Slice(f.values, func(i, j int) bool {
+			for orderBy := 0; orderBy < len(f.opt.OrderBy); orderBy++ {
+				isAsc := f.opt.OrderBy[orderBy].IsAsc
+				result, areEqual, _ := shouldComeBefore(
+					f.values[i].OrderBy[orderBy].Value,
+					f.values[j].OrderBy[orderBy].Value,
+					isAsc,
+				)
+				if !areEqual {
+					return result
+				}
 			}
-		}
+			return false
+		})
 	}
 	if f.opt != nil && f.opt.Limit != nil {
 		minLen := int64(len(f.values))
diff --git a/internal/function_window_option.go b/internal/function_window_option.go
index 19da038..0bb5157 100644
--- a/internal/function_window_option.go
+++ b/internal/function_window_option.go
@@ -406,31 +406,22 @@ func (s *WindowFuncAggregatedStatus) Done(cb func([]Value, int, int) error) erro
 	sortedValues := make([]*WindowOrderedValue, len(values))
 	copy(sortedValues, values)
 	if len(sortedValues) != 0 {
-		for orderBy := 0; orderBy < len(sortedValues[0].OrderBy); orderBy++ {
-			isAsc := sortedValues[0].OrderBy[orderBy].IsAsc
-			if isAsc {
-				sort.Slice(sortedValues, func(i, j int) bool {
-					if sortedValues[i].OrderBy[orderBy].Value == nil {
-						return true
+		orderByObjects := sortedValues[0].OrderBy
+		if orderByObjects != nil && len(orderByObjects) != 0 {
+			sort.Slice(sortedValues, func(i, j int) bool {
+				for orderBy := 0; orderBy < len(orderByObjects); orderBy++ {
+					isAsc := orderByObjects[orderBy].IsAsc
+					result, areEqual, _ := shouldComeBefore(
+						sortedValues[i].OrderBy[orderBy].Value,
+						sortedValues[j].OrderBy[orderBy].Value,
+						isAsc,
+					)
+					if !areEqual {
+						return result
 					}
-					if sortedValues[j].OrderBy[orderBy].Value == nil {
-						return false
-					}
-					cond, _ := sortedValues[i].OrderBy[orderBy].Value.LT(sortedValues[j].OrderBy[orderBy].Value)
-					return cond
-				})
-			} else {
-				sort.Slice(sortedValues, func(i, j int) bool {
-					if sortedValues[i].OrderBy[orderBy].Value == nil {
-						return true
-					}
-					if sortedValues[j].OrderBy[orderBy].Value == nil {
-						return false
-					}
-					cond, _ := sortedValues[i].OrderBy[orderBy].Value.GT(sortedValues[j].OrderBy[orderBy].Value)
-					return cond
-				})
-			}
+				}
+				return false
+			})
 		}
 	}
 	s.SortedValues = sortedValues
diff --git a/internal/util.go b/internal/util.go
index 378bb49..92f796a 100644
--- a/internal/util.go
+++ b/internal/util.go
@@ -82,3 +82,42 @@ func modifyTimeZone(t time.Time, loc *time.Location) (time.Time, error) {
 func timeFromUnixNano(unixNano int64) time.Time {
 	return time.Unix(0, unixNano)
 }
+
+// checkOrderBy checks if value2 should come before value1 (first bool value).
+// Second bool is to determine if values are equal
+func shouldComeBefore(value1, value2 Value, isAscending bool) (bool, bool, error) {
+
+	if value1 == nil && value2 == nil {
+		return false, true, nil
+	}
+
+	if value1 == nil {
+		return true, false, nil
+	}
+	if value2 == nil {
+		return false, false, nil
+	}
+
+	v, err := value1.EQ(value2)
+	if err != nil {
+		return false, false, err
+	}
+
+	if v {
+		return false, true, nil
+	}
+
+	if isAscending {
+		v, err = value1.LT(value2)
+		if err != nil {
+			return false, false, err
+		}
+		return v, false, nil
+	}
+
+	v, err = value1.GT(value2)
+	if err != nil {
+		return false, false, err
+	}
+	return v, false, nil
+}