# tAddCRCRow

Provides a unique ID which helps improving the quality of processed data. CRC stands for Cyclical Redundancy Checking.

tAddCRCRow calculates a surrogate key based on one or several columns and adds it to the defined schema.

This component is not shipped with your Talend Studio by default. You need to install it using the Feature Manager. For more information, see [Installing features using the Feature Manager](https://help.qlik.com/talend/r/en-US/8.0/studio-user-guide/install-features-to-talend-studio).

## tAddCRCRow Standard properties

These properties are used to configure tAddCRCRow running in the Standard Job framework.

The Standard tAddCRCRow component belongs to the Data Quality family.

The component in this framework is available in all Talend products.

## Basic settings

| Properties | Description |
| --- | --- |
| Schema and Edit<br>Schema | <ul> <li> <p>A schema is a row description. it defines the number of fields to be processed and								passed on to the next component. The schema is either <span>Built-in</span> or stored remotely in the									<span>Repository</span>.</p> <p>In this component, a new CRC column is automatically added.</p> </li> <li> <p> <span>Built-in</span>: The schema will be								created and stored locally for this component only. For more information about a component schema in its <span>Basic settings</span> tab, see <a href="https://help.qlik.com/talend/r/en-US/8.0/studio-user-guide/basic-settings-tab" target="_blank">Basic settings tab</a>.</p> </li> <li> <p> <span>Repository</span>: The schema already								exists and is stored in the Repository, hence can be reused in								various projects and Job designs. For more information about a component schema in its <span>Basic settings</span> tab, see <a href="https://help.qlik.com/talend/r/en-US/8.0/studio-user-guide/basic-settings-tab" target="_blank">Basic settings tab</a>.</p> </li> </ul> |
| Implication | Select the check box facing the relevant columns to be used for<br>the surrogate key checksum. |

## Advanced Settings

| Properties | Description |
| --- | --- |
| CRC type | Select a CRC type in the list. The longer the CRC, the least<br>overlap you will have. |
| tStat<br>Catcher<br>Statistics | Select this check box to collect log data at the component<br>level. |

## Global Variables

| Variables | Description |
| --- | --- |
| Global Variables | NB\_LINE: the number<br>of rows read by an input component or transferred to an output component. This is an<br>After variable and it returns an integer.<br><br><br>ERROR\_MESSAGE: the error message generated by the<br>component when an error occurs. This is an After variable and it returns a string. This<br>variable functions only if the Die on error checkbox is<br>cleared, if the component has this checkbox.<br><br>A Flow variable functions during the execution of a component<br>while an After variable functions after the execution of the component.<br><br>To fill up a field or expression with a variable, press Ctrl+Space to access the variable list and choose the variable to use from<br>it.<br><br>For more information about variables, see [Using contexts and variables](https://help.qlik.com/talend/r/en-US/8.0/studio-user-guide/contexts-and-variables). |

## Usage

| Usage guidance | Description |
| --- | --- |
| **Usage rule** | This component is an intermediary step. It requires an input flow<br>as well as an output. |
| Limitation | Due to license incompatibility, one or more JARs required to use this component<br>are not provided. You can install the missing JARs for this particular component by<br>clicking the Install button on the Component tab view. You can also find out and add all missing<br>JARs easily on the Modules tab in the Integration perspective of Talend Studio. For<br>details, see [Installing external modules](https://help.qlik.com/talend/r/en-US/8.0/studio-user-guide/installing-external-modules). |

**Related concepts**

* [Adding a surrogate key to a file](https://help.qlik.com/talend/en-US/components/8.0/identification/taddcrcrow-tfileinputdelimited-tlogrow-tlogrow-adding-surrogate-key-to-file-standard-component-this)