---
title: "FirstDiscreteByInvertedIndex"
slug: "firstdiscretebyinvertedindex"
updated: 2022-02-10T17:53:28Z
published: 2022-02-10T17:53:28Z
canonical: "docs.datajet.app/firstdiscretebyinvertedindex"
---

> ## 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.

# FirstDiscreteByInvertedIndex

## General: FirstDiscreteByInvertedIndex

## Creates a flag field where the first occurrence of each unique value in the specified field is set to 1 – but derived as if the table by in descending order of the sort field.

## Purpose

Use this function to:

- Reverse sort data before flagging first record that has a unique value
- Flag the latest occurrence of a value in a Recordset

## Return Value

| Property | Value |
| --- | --- |
| **FieldType** | Integer |
| **FieldSize** | Low |
| **DataType** | Discrete |
| **DataSize** | Byte |

```shell
Example Return Value: 0 , 1, null
```

![](https://cdn.document360.io/73b6469b-c1e4-47e9-aa65-986c8ebd17ca/Images/Documentation/Gen_FDByInvertedIndex_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. |
| **Function** | "function":"firstdiscretebyinvertedindex" | FirstDiscreteByInvertedIndex |
| **Distinct Key** | “p1”: “DistinctKeyFieldName” | Required. *Supports:* - **DataType**: Must be a Discrete DataType from the target table - will not work with continuous fields. Once the data has been “reverse sorted” by the **Sort Field**, the *first occurrence* of each unique value of Distinct Key will be flagged. If a continuous field needs to be used, it may be possible to derive a discrete field from the continuous field using the CONCAT function. It may be necessary to apply a filter to reduce the number of discrete values. |
| **Sort Field** | “p2”:"SortFieldName" | Required. *Supports:* - **DataType**: Must be a Discrete DataType from the target table - will not work with continuous fields. Field used to determine the reverse sort order of the Recordset. The first occurrence of **Distinct Key** in the sorted Recordset will be flagged. |

## JSON Sample

```json
{
  "method": "BuildBakedField",
  "project": "D3",
  "targetTable": "transactions",
  "overwrite": true,
  "name": "FD_LastProduct_ByDate",
  "function": "firstdiscretebyinvertedindex",
  "p1": "product",
  "p2": "date"
}
```

## Usage Notes

See Also:

- Engineering | Expression Field
- FirstDiscrete (General Functions)
- FirstDiscreteByIndex (General Functions)

## Example

| Example | Details |
| --- | --- |
| **Description** |  |
| **Input** | - Table: = [transactions] - Filter: = [No Filter] - **Function: = FirstDiscreteByInvertedIndex** - Distinct Key:= product - Sort Field:= date - Name: =FD_LastProduct_ByDate |
| **Sample** | ![](https://cdn.document360.io/73b6469b-c1e4-47e9-aa65-986c8ebd17ca/Images/Documentation/Gen_FDByInvertedIndex_Example.png) |