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Changes-on-null-desc #2117

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Jun 6, 2023
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2 changes: 1 addition & 1 deletion docs-2.0/3.ngql-guide/10.tag-statements/1.create-tag.md
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Expand Up @@ -34,7 +34,7 @@ CREATE TAG [IF NOT EXISTS] <tag_name>
|`<tag_name>`|1. Each tag name in the graph space must be **unique**. <br>2. Tag names cannot be modified after they are set.<br>3. Tag names cannot start with a number; they support 1-4 byte UTF-8 encoded characters, including English letters (case sensitive), numbers, Chinese characters, etc., but do not support special characters other than underscores. To use special characters, reserved keywords, or start with a number in a tag name, enclose them in backticks (\`), and do not use periods (`.`) in a tag name. For more information, see [Keywords and reserved words](../../3.ngql-guide/1.nGQL-overview/keywords-and-reserved-words.md). **Note**: If you name a tag in Chinese and encounter a `SyntaxError`, you need to quote the Chinese characters with backticks (\`).|
|`<prop_name>`|The name of the property. It must be unique for each tag. The rules for permitted property names are the same as those for tag names.|
|`<data_type>`|Shows the data type of each property. For a full description of the property data types, see [Data types](../3.data-types/1.numeric.md) and [Boolean](../3.data-types/2.boolean.md).|
|`NULL \| NOT NULL`|Specifies if the property supports `NULL | NOT NULL`. The default value is `NULL`. `DEFAULT` must be specified if `NOT NULL` is set.|
|`NULL \| NOT NULL`|Specifies if the property supports `NULL | NOT NULL`. The default value is `NULL`. |
|`DEFAULT`|Specifies a default value for a property. The default value can be a literal value or an expression supported by NebulaGraph. If no value is specified, the default value is used when inserting a new vertex.|
|`COMMENT`|The remarks of a certain property or the tag itself. The maximum length is 256 bytes. By default, there will be no comments on a tag.|
|`TTL_DURATION`|Specifies the life cycle for the property. The property that exceeds the specified TTL expires. The expiration threshold is the `TTL_COL` value plus the `TTL_DURATION`. The default value of `TTL_DURATION` is `0`. It means the data never expires.|
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