diff --git a/Providers/FreeSql.Provider.QuestDb/QuestDbGlobalExtensions.cs b/Providers/FreeSql.Provider.QuestDb/QuestDbGlobalExtensions.cs
index aed7de90b..92483dd93 100644
--- a/Providers/FreeSql.Provider.QuestDb/QuestDbGlobalExtensions.cs
+++ b/Providers/FreeSql.Provider.QuestDb/QuestDbGlobalExtensions.cs
@@ -113,15 +113,13 @@ public static partial class QuestDbGlobalExtensions
     /// <param name="unit">单位</param>
     /// <param name="alignToCalendar">对准日历</param>
     /// <returns></returns>
-    public static ISelect<T> SampleBy<T>(this ISelect<T> select, double time, SampleUnits unit, bool alignToCalendar = false)
+    public static ISelect<T> SampleBy<T>(this ISelect<T> select, double time, SampleUnit unit, bool alignToCalendar = false)
     {
-        var _unit = Enum.GetName(typeof(SampleUnits), unit);
         SampleByExtension.IsExistence.Value = true;
         var samoleByTemple = $"{Environment.NewLine}SAMPLE BY {{0}}{{1}} {{2}}";
         string alignToCalendarTemple = "";
-        if (alignToCalendar)
-            alignToCalendarTemple = "ALIGN TO CALENDAR ";
-        SampleByExtension.SamoleByString.Value = string.Format(samoleByTemple, time.ToString(), _unit, alignToCalendarTemple);
+        if (alignToCalendar) alignToCalendarTemple = "ALIGN TO CALENDAR ";
+        SampleByExtension.SamoleByString.Value = string.Format(samoleByTemple, time.ToString(), (char)unit, alignToCalendarTemple);
         return select;
     }
 
diff --git a/Providers/FreeSql.Provider.QuestDb/QuestDbUtils.cs b/Providers/FreeSql.Provider.QuestDb/QuestDbUtils.cs
index ea2c4147e..4d71da002 100644
--- a/Providers/FreeSql.Provider.QuestDb/QuestDbUtils.cs
+++ b/Providers/FreeSql.Provider.QuestDb/QuestDbUtils.cs
@@ -301,41 +301,15 @@ namespace FreeSql.QuestDb
 
 namespace FreeSql
 {
-    public enum SampleUnits
+    public enum SampleUnit
     {
-        /// <summary>
-        /// 微秒
-        /// </summary>
-        U,
-
-        /// <summary>
-        /// 毫秒
-        /// </summary>
-        T,
-
-        /// <summary>
-        /// 秒
-        /// </summary>
-        s,
-
-        /// <summary>
-        /// 分钟
-        /// </summary>
-        m,
-
-        /// <summary>
-        /// 时
-        /// </summary>
-        h,
-
-        /// <summary>
-        /// 天
-        /// </summary>
-        d,
-
-        /// <summary>
-        /// 月
-        /// </summary>
-        M
+        microsecond = 'U',
+        millisecond = 'T',
+        second = 's',
+        minute = 'm',
+        hour = 'h',
+        day = 'd',
+        month = 'M',
+        year = 'y',
     }
 }
\ No newline at end of file