# cfxdm - dm:mergecolumns

**dm:mergecolumns:** This cfxdm tag allows the user to select multiple columns using include or exclude columns options using a regular expression format and merge them into a single target column.

**dm:mergecolumns** syntax**:** 

* **include (**Mandatory**):** Specify a column or columns in regular expression format to include matched columns.
* **exclude (**Optional**):** Specify a column or columns in regular expression format to exclude matched columns.
* **to** (Mandatory): Target column for merged data from selected one or more columns.

{% hint style="info" %}
**Note:** After merging multiple columns into a single column, it will remove source columns from the final output.
{% endhint %}

In the below example, for a reference, we are going to use **Elasticsearch** as an extension to query **Netflow data** and ingest it into **dm:mergecolumns** to select specific columns using include/exclude or both together and merge them into a single target column.

Enter the below command to select **Netflow tag (#es:netflow**). (In this example, **es** name is used as a label to identify Elasticsearch extension and it's tags that are pointing to Netflow data index. The label is defined while adding the extension in cfxdx configuration file or through UI)

```
tag #es:netflow
```

![](/files/-MViGo-mzJmGerXr3d_1)

{% hint style="info" %}
Netflow tag includes many columns, in this exercise, we are going to use only few selective columns. For include / exclude regular expressions examples, please refer [**dm:selectcolumns**](/rda/rda-userguide/rda-data-management-cfxdm/cfxdm-dm-selectcolumns.md) documentation. 
{% endhint %}

**Example 1:** Select three columns using include option from Netflow tag and merge them into a single column.

Get the TCP protocol data from Elasticsearch Netflow tag (**#es:netflow**) for last 1 hour and select the below three columns and merge them (values) together into a single target column.

**Source Columns:**

* flow\.client\_addr
* flow\.server\_addr
* flow\.service\_port

**Target Column:**

* flow\.unique**\_**id

Get the data with above three source columns for a quick data review.

```
data `flow.ip_protocol` contains 'TCP' and `@timestamp` after -1 hour GET `flow.client_addr`, `flow.server_addr`, `flow.service_port`
```

![](/files/-MViLO0TgMy2qMVv7yU6)

Extend the query by ingesting the above queried data selecting three columns into **dm:mergecolumns** tag, include all three columns and merge them into a single column as explained above.

```
data `flow.ip_protocol` contains 'TCP' and `@timestamp` after -1 hour GET `flow.client_addr`, `flow.server_addr`, `flow.service_port` --> dm:mergecolumns include = 'flow.client_addr|flow.server_addr|flow.service_port' & to = 'flow.unique_id'
```

![](/files/-MViOP2UBLWIRBhdvS_3)


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