diff --git a/plugins/outputs/clickhouse/clickhouse.go b/plugins/outputs/clickhouse/clickhouse.go
index 1a53b92..0afaae5 100644
--- a/plugins/outputs/clickhouse/clickhouse.go
+++ b/plugins/outputs/clickhouse/clickhouse.go
@@ -174,16 +174,17 @@ func (ch *ClickHouse) valueToDatatype(value interface{}) string {
 	return datatype
 }
 
+func (ch *ClickHouse) toNullableType(pair *orderedmap.Pair[string, string]) string {
+	if pair.Key != "host" && pair.Key != ch.TimestampColumn && pair.Key != "measurement" {
+		return fmt.Sprintf("Nullable(%s)", pair.Value)
+	}
+	return pair.Value
+}
+
 func (ch *ClickHouse) generateCreateTable(tablename string, columns *orderedmap.OrderedMap[string, string]) string {
 	columnDefs := make([]string, 0, columns.Len())
-
 	for pair := columns.Oldest(); pair != nil; pair = pair.Next() {
-		columnType := pair.Value
-		if pair.Key != "host" && pair.Key != ch.TimestampColumn && pair.Key != "measurement" {
-			columnType = fmt.Sprintf("Nullable(%s)", pair.Value)
-		}
-
-		columnDefs = append(columnDefs, fmt.Sprintf("%s %s", quoteIdent(pair.Key), columnType))
+		columnDefs = append(columnDefs, fmt.Sprintf("%s %s", quoteIdent(pair.Key), ch.toNullableType(pair)))
 	}
 
 	orderBy := make([]string, 0, 3)
@@ -210,21 +211,24 @@ func (ch *ClickHouse) generateCreateTable(tablename string, columns *orderedmap.
 
 func (ch *ClickHouse) generateAlterTable(tablename string, columns *orderedmap.OrderedMap[string, string]) string {
 	alterDefs := make([]string, 0, columns.Len())
+	modifyDefs := make([]string, 0, columns.Len())
 
 	for pair := columns.Oldest(); pair != nil; pair = pair.Next() {
-		columnType := pair.Value
-		if pair.Key != "host" && pair.Key != ch.TimestampColumn && pair.Key != "measurement" {
-			columnType = fmt.Sprintf("Nullable(%s)", pair.Value)
-		}
+		columnType := ch.toNullableType(pair)
 
 		alterDefs = append(alterDefs, fmt.Sprintf("ADD COLUMN IF NOT EXISTS %s %s",
 			quoteIdent(pair.Key),
 			columnType))
+
+		modifyDefs = append(modifyDefs, fmt.Sprintf("MODIFY COLUMN IF EXISTS %s %s",
+			quoteIdent(pair.Key),
+			columnType))
 	}
 
-	return fmt.Sprintf("ALTER TABLE %s %s",
+	return fmt.Sprintf("ALTER TABLE %s %s, %s",
 		quoteIdent(tablename),
-		strings.Join(alterDefs, ","))
+		strings.Join(alterDefs, ","),
+		strings.Join(modifyDefs, ","))
 }
 
 func (ch *ClickHouse) ensureTable(tablename string, columns *orderedmap.OrderedMap[string, string]) error {
@@ -251,21 +255,22 @@ func (ch *ClickHouse) ensureTable(tablename string, columns *orderedmap.OrderedM
 		break
 	}
 
-	tableColumns := make(map[string]struct{})
+	tableColumns := make(map[string]string)
 	for res.Next() {
 		var name string
+		var dtype string
 		var _i string
 
-		err = res.Scan(&name, &_i, &_i, &_i, &_i, &_i, &_i)
+		err = res.Scan(&name, &dtype, &_i, &_i, &_i, &_i, &_i)
 		if err != nil {
 			return err
 		}
 
-		tableColumns[name] = struct{}{}
+		tableColumns[name] = dtype
 	}
 
 	for pair := columns.Oldest(); pair != nil; pair = pair.Next() {
-		if _, ok := tableColumns[pair.Key]; !ok {
+		if _, ok := tableColumns[pair.Key]; !ok || tableColumns[pair.Key] != ch.toNullableType(pair) {
 			_, err = ch.db.Exec(ch.generateAlterTable(tablename, columns))
 			if err != nil {
 				return err
@@ -289,7 +294,7 @@ func (ch *ClickHouse) generateInsert(tablename string, columns *orderedmap.Order
 
 	return fmt.Sprintf("INSERT INTO %s (%s) VALUES %s",
 		quoteIdent(tablename),
-		strings.Join(quotedColumns, ", "),
+		strings.Join(quotedColumns, ","),
 		placeholders)
 }
 
@@ -418,12 +423,6 @@ func (ch *ClickHouse) WriteSingleTable(metrics []telegraf.Metric) error {
 			columns.Set(colName, ch.valueToDatatype(field.Value))
 		}
 
-		for pair := columns.Oldest(); pair != nil; pair = pair.Next() {
-			if _, ok := metricEntry[pair.Key]; !ok {
-				metricEntry[pair.Key] = pair.Value
-			}
-		}
-
 		metricsData = append(metricsData, metricEntry)
 	}
 	ch.Log.Infof("Prepared %d metrics for writing in %s\n", len(metrics), time.Since(start))