---
title: "DescendingIndex"
slug: "descendingindex"
updated: 2022-02-10T19:23:16Z
published: 2022-02-10T19:23:16Z
canonical: "docs.datajet.app/descendingindex"
---

> ## Documentation Index
> Fetch the complete documentation index at: https://docs.datajet.app/llms.txt
> Use this file to discover all available pages before exploring further.

# DescendingIndex

## General: DescendingIndex

## Assigns an integer to each unique value in the field, working in reverse order.

Creates an Integer field with values N to 1, where N is the number of discrete values in the source field.

## Purpose

Use this function to:

- Reverse sort unique values in a field
- Transform a field into an integer for use with integer engineering functions

## Return Value

| Property | Value |
| --- | --- |
| **FieldType** | Integer / LongInteger |
| **FieldSize** | Low / Med / High |
| **DataType** | Discrete |
| **DataSize** | Byte / Short / Integer |

```shell
Example Return Value: N......1
```

![](https://cdn.document360.io/73b6469b-c1e4-47e9-aa65-986c8ebd17ca/Images/Documentation/Gen_DescIndex_Sample.PNG)

## Parameters

| Parameter | JSON | Description |
| --- | --- | --- |
| **Table** | “targetTable”: “MyTableName” | The target table on which the new field will be created |
| **Filter** | “dataset”: {DataSet_JSON} | Optional. If a filter is applied, records not in the filter recordset will be returned as null. Use a filter to exclude records from the source field. If the source field has too many discrete values to create a DescendingIndex, excluding some records may reduce the index size enough for a discrete index to be created.To specify records to Exclude: 1. Select the records to be excluded and drag them into the HotBar 2. Right-click and choose the Invert function 3. Add the resulting Recordset as a filter |
| **Function** | "function":"descendingindex" | DescendingIndex |
| **Source Field** | “p1”: “SourceFieldName” | Required. The Discrete (i.e., non-continuous) field from which to create the index. If it is necessary to create an index from a continuous field, depending on the field contents, the CONCAT function can sometimes be used to create a discrete copy of the continuous field. If the continuous field is a numeric field, the output from the CONCAT function can be cast back into a numeric field using the WILDICAST function. Strings can be cast as date fields using the DateFromString function. |
| **Treat Null as Zero** | "nullIsZero": true "nullIsZero": false | True/False. Default = False If true, then any null values in the input fields will be treated as if they have a value of 0. |

## JSON Sample

```json
{
  "method": "BuildBakedField",
  "project": "D3",
  "targetTable": "transactions",
  "overwrite": true,
  "name": "DescIndex_date",
  "function": "descendingindex",
  "p1": "date"
}
```

## Usage Notes

The function only works on Discrete source fields. See CONCAT, WILDICAST and DATEFROMSTRING if it is necessary to create an index from a Continuous field.

If a filter is applied, records which are not in the filter will be stored as NULL in the new field. Applying a filter may reduce the number of discrete values in a continuous field sufficiently to create a discrete index.

The maximum number of discrete values in a discrete index is 1,000,000

For more information on field and data types, see **Field Types and Data Types**

See Also:

- Engineering | Expression Field
- CONCAT   (String Function)
- WILDICAST (String Function)
- DATEFROMSTRING   (String Function)

## Example

| Example | Details |
| --- | --- |
| **Description** | Create a descending index from average spend |
| **Input** | - Table: = [customer] - Filter: = [No Filter] - **Function: = DescendingIndex** - Source Field:= avgl_spend - Name: =spend_descend |
| **Sample** | ![](https://cdn.document360.io/73b6469b-c1e4-47e9-aa65-986c8ebd17ca/Images/Documentation/Gen_DescIndex_Example.png) |