diff --git a/main.go b/main.go
index 0ed1369..379ac62 100644
--- a/main.go
+++ b/main.go
@@ -15,15 +15,15 @@ import (
 
 type Payload struct {
 	T   string `json:"t"`
-	Dt1 int    `json:"dt1"`
-	Dt2 int    `json:"dt2"`
-	Rt1 int    `json:"rt1"`
-	Rt2 int    `json:"rt2"`
+	Dt1 *int   `json:"dt1"`
+	Dt2 *int   `json:"dt2"`
+	Rt1 *int   `json:"rt1"`
+	Rt2 *int   `json:"rt2"`
 	D   int    `json:"d"`
 	R   int    `json:"r"`
 	F   int    `json:"f"`
 	Fl  int    `json:"fl"`
-	G   int    `json:"g"`
+	G   *int   `json:"g"`
 	V1  int    `json:"v1"`
 	V2  int    `json:"v2"`
 	V3  int    `json:"v3"`
@@ -88,6 +88,18 @@ func main() {
 	select {}
 }
 
+var prevDt1, prevDt2, prevRt1, prevRt2, prevG int
+
+func updateFieldIfChanged(currentValue *int, previousValue *int) *int {
+	if currentValue != nil && *currentValue == *previousValue {
+		return nil // No change, so we prepare to insert a NULL
+	} else if currentValue != nil {
+		*previousValue = *currentValue // Update the previous value to the current one
+		return currentValue
+	}
+	return currentValue // Return the original value if it's nil
+}
+
 func mqttMessageHandler(client mqtt.Client, msg mqtt.Message) {
 	// Parse JSON payload
 	var payload Payload
@@ -104,6 +116,12 @@ func mqttMessageHandler(client mqtt.Client, msg mqtt.Message) {
 		return
 	}
 
+	payload.Dt1 = updateFieldIfChanged(payload.Dt1, &prevDt1)
+	payload.Dt2 = updateFieldIfChanged(payload.Dt2, &prevDt2)
+	payload.Rt1 = updateFieldIfChanged(payload.Rt1, &prevRt1)
+	payload.Rt2 = updateFieldIfChanged(payload.Rt2, &prevRt2)
+	payload.G = updateFieldIfChanged(payload.G, &prevG)
+
 	// Insert data into PostgreSQL
 	err = insertData(timestamp, payload)
 	if err != nil {