diff --git a/sql/src/influxql/provider.rs b/sql/src/influxql/provider.rs
index 7694b26c1b..33569befe2 100644
--- a/sql/src/influxql/provider.rs
+++ b/sql/src/influxql/provider.rs
@@ -125,12 +125,14 @@ fn map_column_to_influx_column(
     is_timestamp_key: bool,
 ) -> Result<InfluxColumnType> {
     if is_timestamp_key {
-        map_column_to_influx_time_column(column)
-    } else if column.is_tag {
-        map_column_to_influx_tag_column(column)
-    } else {
-        map_column_to_influx_field_column(column)
+        return map_column_to_influx_time_column(column);
+    }
+
+    if column.is_tag {
+        return map_column_to_influx_tag_column(column);
     }
+
+    map_column_to_influx_field_column(column)
 }
 
 fn map_column_to_influx_time_column(column: &ColumnSchema) -> Result<InfluxColumnType> {
@@ -144,6 +146,7 @@ fn map_column_to_influx_time_column(column: &ColumnSchema) -> Result<InfluxColum
     }
 }
 
+// TODO: support more tag types.
 fn map_column_to_influx_tag_column(column: &ColumnSchema) -> Result<InfluxColumnType> {
     // Tag column
     if matches!(column.data_type, DatumKind::String) && column.is_nullable {
@@ -156,6 +159,7 @@ fn map_column_to_influx_tag_column(column: &ColumnSchema) -> Result<InfluxColumn
     }
 }
 
+// TODO: support more field types.
 fn map_column_to_influx_field_column(column: &ColumnSchema) -> Result<InfluxColumnType> {
     if column.is_nullable {
         match column.data_type {