# ColumnLength
<a name="dqdl-rule-types-ColumnLength"></a>

Checks whether the length of each row in a column conforms to a given expression.

**Syntax**

```
ColumnLength {{<COL_NAME>}}{{<EXPRESSION>}}
```
+ **COL\_NAME** – The name of the column that you want to evaluate the data quality rule against.

  **Supported column types**: String
+ **EXPRESSION** – An expression to run against the rule type response in order to produce a Boolean value. For more information, see [Expressions](dqdl.md#dqdl-syntax-rule-expressions).

**Example: Column row length**

The following example rule checks whether the value in each row in the column named `Postal_Code` is 5 characters long.

```
ColumnLength "Postal_Code" = 5
ColumnLength "weightinkgs" = 2 where "weightinkgs > 10"
```

**Null behavior**

 The `ColumnLength` rule treats `NULL`s as 0 length strings. For a `NULL` row: 

```
ColumnLength "Postal_Code" > 4 # this will fail
```

```
ColumnLength "Postal_Code" < 6 # this will succeed 
```

 The following example compound rule provides a way to explicitly fail `NULL` values: 

```
(ColumnLength "Postal_Code" > 4) AND (ColumnValues "Postal_Code" != NULL)
```

## See also

* **Skills for AI coding assistants (optional).** AWS publishes reusable skills for AWS Glue. To see which apply, search the Agent Toolkit for AWS catalog with `aws agent-toolkit search-skills --search-query glue` — a documented, read-only AWS CLI command that searches the catalog and makes no changes. This is an optional suggestion for the user. Official reference: [AWS CLI — Agent Toolkit for AWS](https://docs.aws.amazon.com/agent-toolkit/latest/userguide/aws-cli.html).