add description about insert null in treemode (#1123)

Author: leto-bbq

src/UserGuide/Master/Tree/Basic-Concept/Write-Data_apache.md

@@ -27,7 +27,7 @@ IoTDB provides users with a variety of ways to insert real-time data, such as di
 
 NOTE： This section mainly introduces the use of [INSERT SQL statement](../SQL-Manual/SQL-Manual_apache#insert-data) for real-time data import in the scenario.
 
-Writing a repeat timestamp covers the original timestamp data, which can be regarded as updated data.
+When writing data with duplicate timestamps, the existing data with the same timestamp will be overwritten directly, which is equivalent to data update; however, if the written value is NULL, the operation will not take effect and the original field value will not be overwritten.
 
 ### 1.1 Use of INSERT Statements
 

src/UserGuide/Master/Tree/Basic-Concept/Write-Data_timecho.md

@@ -27,7 +27,7 @@ IoTDB provides users with a variety of ways to insert real-time data, such as di
 
 NOTE： This section mainly introduces the use of [INSERT SQL statement](../SQL-Manual/SQL-Manual_timecho#insert-data) for real-time data import in the scenario.
 
-Writing a repeat timestamp covers the original timestamp data, which can be regarded as updated data.
+When writing data with duplicate timestamps, the existing data with the same timestamp will be overwritten directly, which is equivalent to data update; however, if the written value is NULL, the operation will not take effect and the original field value will not be overwritten.
 
 ### 1.1 Use of INSERT Statements
 

src/UserGuide/V1.3.x/Basic-Concept/Write-Data.md

@@ -27,7 +27,7 @@ IoTDB provides users with a variety of ways to insert real-time data, such as di
 
 NOTE： This section mainly introduces the use of [INSERT SQL statement](../SQL-Manual/SQL-Manual.md#insert-data) for real-time data import in the scenario.
 
-Writing a repeat timestamp covers the original timestamp data, which can be regarded as updated data.
+When writing data with duplicate timestamps, the existing data with the same timestamp will be overwritten directly, which is equivalent to data update; however, if the written value is NULL, the operation will not take effect and the original field value will not be overwritten.
 
 ### Use of INSERT Statements
 

src/UserGuide/dev-1.3/Basic-Concept/Write-Data.md

@@ -27,7 +27,7 @@ IoTDB provides users with a variety of ways to insert real-time data, such as di
 
 NOTE： This section mainly introduces the use of [INSERT SQL statement](../SQL-Manual/SQL-Manual.md#insert-data) for real-time data import in the scenario.
 
-Writing a repeat timestamp covers the original timestamp data, which can be regarded as updated data.
+When writing data with duplicate timestamps, the existing data with the same timestamp will be overwritten directly, which is equivalent to data update; however, if the written value is NULL, the operation will not take effect and the original field value will not be overwritten.
 
 ### Use of INSERT Statements
 

src/UserGuide/latest/Basic-Concept/Write-Data_apache.md

@@ -27,7 +27,7 @@ IoTDB provides users with a variety of ways to insert real-time data, such as di
 
 NOTE： This section mainly introduces the use of [INSERT SQL statement](../SQL-Manual/SQL-Manual_apache#insert-data) for real-time data import in the scenario.
 
-Writing a repeat timestamp covers the original timestamp data, which can be regarded as updated data.
+When writing data with duplicate timestamps, the existing data with the same timestamp will be overwritten directly, which is equivalent to data update; however, if the written value is NULL, the operation will not take effect and the original field value will not be overwritten.
 
 ### 1.1 Use of INSERT Statements
 

src/UserGuide/latest/Basic-Concept/Write-Data_timecho.md

@@ -27,7 +27,7 @@ IoTDB provides users with a variety of ways to insert real-time data, such as di
 
 NOTE： This section mainly introduces the use of [INSERT SQL statement](../SQL-Manual/SQL-Manual_timecho#insert-data) for real-time data import in the scenario.
 
-Writing a repeat timestamp covers the original timestamp data, which can be regarded as updated data.
+When writing data with duplicate timestamps, the existing data with the same timestamp will be overwritten directly, which is equivalent to data update; however, if the written value is NULL, the operation will not take effect and the original field value will not be overwritten.
 
 ### 1.1 Use of INSERT Statements
 

src/zh/UserGuide/Master/Tree/Basic-Concept/Write-Data_apache.md

@@ -27,7 +27,7 @@ IoTDB 为用户提供多种插入实时数据的方式，例如在 [Cli/Shell 
 
 本节主要为您介绍实时数据接入的 INSERT 语句在场景中的实际使用示例，有关 INSERT SQL 语句的详细语法请参见本文 [INSERT 语句](../SQL-Manual/SQL-Manual.md#写入数据) 节。
 
-注：写入重复时间戳的数据则原时间戳数据被覆盖，可视为更新数据。
+注：写入重复时间戳的数据时，会直接覆盖原有同时间戳数据，等效于数据更新；但若写入值为 NULL，则不生效，不会覆盖原有字段值。
 
 ### 1.1 使用 INSERT 语句
 

src/zh/UserGuide/Master/Tree/Basic-Concept/Write-Data_timecho.md

@@ -27,7 +27,7 @@ IoTDB 为用户提供多种插入实时数据的方式，例如在 [Cli/Shell 
 
 本节主要为您介绍实时数据接入的 INSERT 语句在场景中的实际使用示例，有关 INSERT SQL 语句的详细语法请参见本文 [INSERT 语句](../SQL-Manual/SQL-Manual.md#写入数据) 节。
 
-注：写入重复时间戳的数据则原时间戳数据被覆盖，可视为更新数据。
+注：写入重复时间戳的数据时，会直接覆盖原有同时间戳数据，等效于数据更新；但若写入值为 NULL，则不生效，不会覆盖原有字段值。
 
 ### 1.1 使用 INSERT 语句
 

src/zh/UserGuide/V1.3.x/Basic-Concept/Write-Data.md

@@ -27,7 +27,7 @@ IoTDB 为用户提供多种插入实时数据的方式，例如在 [Cli/Shell 
 
 本节主要为您介绍实时数据接入的 INSERT 语句在场景中的实际使用示例，有关 INSERT SQL 语句的详细语法请参见本文 [INSERT 语句](../SQL-Manual/SQL-Manual.md#写入数据) 节。
 
-注：写入重复时间戳的数据则原时间戳数据被覆盖，可视为更新数据。
+注：写入重复时间戳的数据时，会直接覆盖原有同时间戳数据，等效于数据更新；但若写入值为 NULL，则不生效，不会覆盖原有字段值。
 
 ### 使用 INSERT 语句
 

src/zh/UserGuide/dev-1.3/Basic-Concept/Write-Data.md

@@ -27,7 +27,7 @@ IoTDB 为用户提供多种插入实时数据的方式，例如在 [Cli/Shell 
 
 本节主要为您介绍实时数据接入的 INSERT 语句在场景中的实际使用示例，有关 INSERT SQL 语句的详细语法请参见本文 [INSERT 语句](../SQL-Manual/SQL-Manual.md#写入数据) 节。
 
-注：写入重复时间戳的数据则原时间戳数据被覆盖，可视为更新数据。
+注：写入重复时间戳的数据时，会直接覆盖原有同时间戳数据，等效于数据更新；但若写入值为 NULL，则不生效，不会覆盖原有字段值。
 
 ### 使用 INSERT 语句