modify docs

documentation20/cn/12.taos-sql/docs.md

@@ -1094,7 +1094,7 @@ TDengine支持针对数据的聚合查询。提供支持的聚合和选择函数
 
     应用字段：适合于除时间主列外的任何类型字段。
 
-    适用于：**表**。
+    说明：由于返回数据量未知，考虑到内存因素，为了函数可以正常返回结果，建议不重复的数据量在10万级别，否则会报错。
 
     示例：
     ```mysql
@@ -1596,7 +1596,9 @@ TDengine支持针对数据的聚合查询。提供支持的聚合和选择函数
 
     支持版本：2.6.0.x 之后的版本。
   
-    说明：该函数可以应用在普通表和超级表上。不能和窗口操作一起使用，例如 interval/state_window/session_window 。
+    说明：
+    - 该函数可以应用在普通表和超级表上。不能和窗口操作一起使用，例如 interval/state_window/session_window 。
+    - 由于返回数据量未知，考虑到内存因素，为了函数可以正常返回结果，建议不重复的数据量在10万级别，否则会报错。
 
     示例：
     ```mysql

documentation20/en/12.taos-sql/docs.md

@@ -864,6 +864,8 @@ TDengine supports aggregations over data, they are listed below:
 
     Supported version: Version after 2.6.0 .
     
+    Note: Since the amount of returned data is unknown, considering the memory factor, in order to return the result normally, it is recommended that the amount of non repeated data is 100000, otherwise an error will be reported.
+    
     Example:
     ```mysql
     taos> select voltage from d002;
@@ -1215,7 +1217,9 @@ TDengine supports aggregations over data, they are listed below:
 
     Supported version: Version after 2.6.0 .
 
-    Note: This function can be applied to ordinary tables and super tables. Cannot be used with window operations，such as interval/state_window/session_window.
+    Note: 
+    - This function can be applied to ordinary tables and super tables. Cannot be used with window operations，such as interval/state_window/session_window.
+    - Since the amount of returned data is unknown, considering the memory factor, in order to return the result normally, it is recommended that the amount of non repeated data is 100000, otherwise an error will be reported.
     
     Example:
     ```mysql