diff --git a/pkg/datasource/explore_query.go b/pkg/datasource/explore_query.go
index c22d928..d157feb 100644
--- a/pkg/datasource/explore_query.go
+++ b/pkg/datasource/explore_query.go
@@ -55,6 +55,7 @@ func (ds I2b2DataSource) ExploreQueryHandler(userID string, jsonParameters []byt
 		{
 			OutputName: outputNameExploreQueryCount,
 			SharedID:   outputDataObjectsSharedIDs[outputNameExploreQueryCount],
+			Columns:    []string{"count"},
 			IntValue:   &count,
 		}, {
 			OutputName: outputNameExploreQueryPatientList,
diff --git a/pkg/datasource/statistics_query.go b/pkg/datasource/statistics_query.go
index 24958c2..bc74926 100644
--- a/pkg/datasource/statistics_query.go
+++ b/pkg/datasource/statistics_query.go
@@ -42,9 +42,12 @@ func (ds I2b2DataSource) StatisticsQueryHandler(
 		valueVector := []int64{}
 		columns := []string{}
 
-		for _, bucket := range statResult.Buckets {
+		// these are needed to correctly sort the columns during the aggregation
+		labels := generateColumnsLabels(len(statResult.Buckets))
+
+		for i, bucket := range statResult.Buckets {
 			valueVector = append(valueVector, bucket.Count)
-			columns = append(columns, "["+fmt.Sprintf("%f", bucket.LowerBound)+", "+fmt.Sprintf("%f", bucket.HigherBound)+"]")
+			columns = append(columns, "[\""+labels[i]+"\", "+fmt.Sprintf("%f", bucket.LowerBound)+", "+fmt.Sprintf("%f", bucket.HigherBound)+"]")
 		}
 		values = append(values, valueVector)
 
diff --git a/pkg/datasource/survival_query.go b/pkg/datasource/survival_query.go
index a9336ac..fea8cf4 100644
--- a/pkg/datasource/survival_query.go
+++ b/pkg/datasource/survival_query.go
@@ -43,6 +43,7 @@ func (ds I2b2DataSource) SurvivalQueryHandler(userID string, jsonParameters []by
 			{
 				OutputName: outputNameSurvivalQueryResult,
 				SharedID:   outputDataObjectsSharedIDs[outputNameSurvivalQueryResult],
+				Columns:    generateColumnsLabels(len(survivalQueryResult)),
 				IntVector:  survivalQueryResult,
 			},
 		}
diff --git a/pkg/datasource/utils.go b/pkg/datasource/utils.go
new file mode 100644
index 0000000..8878b8e
--- /dev/null
+++ b/pkg/datasource/utils.go
@@ -0,0 +1,20 @@
+package datasource
+
+import (
+	"fmt"
+	"math"
+)
+
+// generateColumnsLabels generates a list containing the string representations of the numbers from 0 to n-1, with the right number of leading 0s.
+// e.g., for n=16 -> ["00", "01, ..., "15"], for n=106 -> ["000", "001", ..., "115"]
+func generateColumnsLabels(n int) []string {
+
+	labels := make([]string, n)
+	figures := int(math.Ceil(math.Log10(float64(n))))
+
+	for i := 0; i < n; i++ {
+		labels[i] = fmt.Sprintf(fmt.Sprintf("%%0%dd", figures), i)
+	}
+
+	return labels
+}