# Add sequence

The **Add sequence** step adds a sequence value to the PDI stream.

A sequence is an ever-changing integer value with a specific start value and increment value. You can either:

* Use a database sequence to generate the next value.
* Generate the value in PDI by using a transformation counter.

PDI-generated sequence values are unique when used in the same transformation and reset to the start value each time you run the transformation.

### Step name

* **Step name**: Specify the unique name of the step on the canvas. **Step name** is set to `Step sequence` by default.

### General

* **Name of value**: Specify the name of the new sequence value field to add to the stream. **Name of value** is set to `valuename` by default.

### Options

Choose one method to generate the sequence.

{% tabs %}
{% tab title="Database sequence" %}
Select **Use DB to generate the sequence?** to drive the sequence by using a database sequence.

| Option                               | Description                                                                                                                                                                             |
| ------------------------------------ | --------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |
| **Use DB to generate the sequence?** | Select this option to drive the sequence by using a database sequence. If you clear this option, **Use counter to calculate sequence?** is selected automatically.                      |
| **Connection**                       | Select the connection where your database sequence resides. If you do not have an existing connection, select **New** or **Wizard**. To modify an existing connection, select **Edit**. |
| **Schema name** (optional)           | Specify the schema name of any related table. Select **Schemas** to choose a schema in the selected connection.                                                                         |
| **Sequence name**                    | Specify the name of the database sequence. Select **Sequences** to choose a sequence in the selected connection.                                                                        |
| {% endtab %}                         |                                                                                                                                                                                         |

{% tab title="Transformation counter" %}
Select **Use counter to calculate sequence?** to generate the sequence in PDI.

| Option                                 | Description                                                                                                                                                                       |
| -------------------------------------- | --------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |
| **Use counter to calculate sequence?** | Select this option to generate the sequence in PDI. This option is selected by default. If you clear this option, **Use DB to generate the sequence?** is selected automatically. |
| **Counter name** (optional)            | Specify the counter name to avoid unique sequencing across multiple steps when multiple steps in a transformation generate the same value name.                                   |
| **Start at value**                     | The start value for the sequence. For example, if **Start at value** is `1`, the sequence starts with `1`.                                                                        |
| **Increment by**                       | The amount by which the sequence increases or decreases.                                                                                                                          |
| **Maximum value**                      | The value to reach before returning the sequence to the **Start at value** setting.                                                                                               |

#### Example

If you set **Start at value** to `1`, **Increment by** to `1`, and **Maximum value** to `3`, the resulting sequence is:

`1, 2, 3, 1, 2, 3, 1, 2`...

If you set **Start at value** to `0`, **Increment by** to `-1`, and **Maximum value** to `-2`, the resulting sequence is:

`0, -1, -2, 0, -1, -2, 0`...
{% endtab %}
{% endtabs %}

### See also

* [**Add value fields changing sequence**](https://wiki.pentaho.com/display/EAI/Add+value+fields+changing+sequence) (Pentaho Wiki). Adds a sequence when the values of a field change. Each time a value of at least one field changes, the added sequence resets to its start value.
* [**Group By**](/pdia-data-integration/pdi-transformation-steps-reference-overview/group-by-landing-page-article.md). Builds aggregates by grouping and generates sequential numbers within rows with repeating values.
* [**Get ID from Slave Server**](https://wiki.pentaho.com/display/EAI/Get+ID+from+Slave+Server) (Pentaho Wiki). Use this step if you need a unique ID in a clustered environment.


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