diff --git a/docs-2.0/3.ngql-guide/10.tag-statements/3.alter-tag.md b/docs-2.0/3.ngql-guide/10.tag-statements/3.alter-tag.md
index 5ed938a18b9..ad8f9820faf 100644
--- a/docs-2.0/3.ngql-guide/10.tag-statements/3.alter-tag.md
+++ b/docs-2.0/3.ngql-guide/10.tag-statements/3.alter-tag.md
@@ -2,12 +2,14 @@
 
 `ALTER TAG` alters the structure of a tag with the given name in a graph space. You can add or drop properties, and change the data type of an existing property. You can also set a [TTL](../8.clauses-and-options/ttl-options.md) (Time-To-Live) on a property, or change its TTL duration.
 
-## Prerequisites
+## Notes
 
 - Running the `ALTER TAG` statement requires some [privileges](../../7.data-security/1.authentication/3.role-list.md) for the graph space. Otherwise, NebulaGraph throws an error.
 
 - Before you alter properties for a tag, make sure that the properties are not indexed. If the properties contain any indexes, the conflict error `[ERROR (-1005)]: Conflict!` will occur when you `ALTER TAG`. For more information on dropping an index, see [DROP INDEX](../14.native-index-statements/6.drop-native-index.md).
 
+- The property name must be unique in a tag. If you add a property with the same name as an existing property or a dropped property, the operation fails.
+
 ## Syntax
 
 ```ngql
diff --git a/docs-2.0/3.ngql-guide/11.edge-type-statements/3.alter-edge.md b/docs-2.0/3.ngql-guide/11.edge-type-statements/3.alter-edge.md
index aae7ec6955b..2577de75a95 100644
--- a/docs-2.0/3.ngql-guide/11.edge-type-statements/3.alter-edge.md
+++ b/docs-2.0/3.ngql-guide/11.edge-type-statements/3.alter-edge.md
@@ -2,12 +2,14 @@
 
 `ALTER EDGE` alters the structure of an edge type with the given name in a graph space. You can add or drop properties, and change the data type of an existing property. You can also set a [TTL](../8.clauses-and-options/ttl-options.md) (Time-To-Live) on a property, or change its TTL duration.
 
-## Prerequisites
+## Notes
 
 - Running the `ALTER EDGE` statement requires some [privileges](../../7.data-security/1.authentication/3.role-list.md) for the graph space. Otherwise, NebulaGraph throws an error.
 
 - Before you alter properties for an edge type, make sure that the properties are not indexed. If the properties contain any indexes, the conflict error `[ERROR (-1005)]: Conflict!` will occur when you `ALTER EDGE`. For more information on dropping an index, see [DROP INDEX](../14.native-index-statements/6.drop-native-index.md).
 
+- The property name must be unique in an edge type. If you add a property with the same name as an existing property or a dropped property, the operation fails.
+
 ## Syntax
 
 ```ngql