# Rule
<a name="API_Rule"></a>

Represents a single data quality requirement that should be validated in the scope of this dataset.

## Contents
<a name="API_Rule_Contents"></a>

**Note**  
In the following list, the required parameters are described first.

 ** CheckExpression **   <a name="databrew-Type-Rule-CheckExpression"></a>
The expression which includes column references, condition names followed by variable references, possibly grouped and combined with other conditions. For example, `(:col1 starts_with :prefix1 or :col1 starts_with :prefix2) and (:col1 ends_with :suffix1 or :col1 ends_with :suffix2)`. Column and value references are substitution variables that should start with the ':' symbol. Depending on the context, substitution variables' values can be either an actual value or a column name. These values are defined in the SubstitutionMap. If a CheckExpression starts with a column reference, then ColumnSelectors in the rule should be null. If ColumnSelectors has been defined, then there should be no column reference in the left side of a condition, for example, `is_between :val1 and :val2`.  
For more information, see [Available checks](https://docs.aws.amazon.com/databrew/latest/dg/profile.data-quality-available-checks.html)   
Type: String  
Length Constraints: Minimum length of 4. Maximum length of 1024.  
Pattern: `^[<>0-9A-Za-z_.,:)(!= ]+$`   
Required: Yes

 ** Name **   <a name="databrew-Type-Rule-Name"></a>
The name of the rule.  
Type: String  
Length Constraints: Minimum length of 1. Maximum length of 128.  
Required: Yes

 ** ColumnSelectors **   <a name="databrew-Type-Rule-ColumnSelectors"></a>
List of column selectors. Selectors can be used to select columns using a name or regular expression from the dataset. Rule will be applied to selected columns.  
Type: Array of [ColumnSelector](API_ColumnSelector.md) objects  
Array Members: Minimum number of 1 item.  
Required: No

 ** Disabled **   <a name="databrew-Type-Rule-Disabled"></a>
A value that specifies whether the rule is disabled. Once a rule is disabled, a profile job will not validate it during a job run. Default value is false.  
Type: Boolean  
Required: No

 ** SubstitutionMap **   <a name="databrew-Type-Rule-SubstitutionMap"></a>
The map of substitution variable names to their values used in a check expression. Variable names should start with a ':' (colon). Variable values can either be actual values or column names. To differentiate between the two, column names should be enclosed in backticks, for example, `":col1": "`Column A`".`   
Type: String to string map  
Key Length Constraints: Minimum length of 2. Maximum length of 128.  
Key Pattern: `^:[A-Za-z0-9_]+$`   
Value Length Constraints: Maximum length of 1024.  
Required: No

 ** Threshold **   <a name="databrew-Type-Rule-Threshold"></a>
The threshold used with a non-aggregate check expression. Non-aggregate check expressions will be applied to each row in a specific column, and the threshold will be used to determine whether the validation succeeds.  
Type: [Threshold](API_Threshold.md) object  
Required: No

## See Also
<a name="API_Rule_SeeAlso"></a>

For more information about using this API in one of the language-specific AWS SDKs, see the following:
+  [AWS SDK for C\$1\$1](https://docs.aws.amazon.com/goto/SdkForCpp/databrew-2017-07-25/Rule) 
+  [AWS SDK for Java V2](https://docs.aws.amazon.com/goto/SdkForJavaV2/databrew-2017-07-25/Rule) 
+  [AWS SDK for Ruby V3](https://docs.aws.amazon.com/goto/SdkForRubyV3/databrew-2017-07-25/Rule)