---
title: "DistinctByKey"
slug: "distinctbykey"
updated: 2022-02-21T17:28:04Z
published: 2022-02-21T17:28:04Z
canonical: "docs.datajet.app/distinctbykey"
---

> ## 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.

# DistinctByKey

## General: DistinctByKey

## Create a flag field, set to true for the first occurrence of each unique value of a key field, for the set of records linked to each key in a primary table.

## Purpose

Use this function to:

- Flag records grouped by their relationship to data in another table

## 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_DistinctByKey_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":"DistinctByKey" | DistinctByKey |
| **Key Table** | “p1”: “PrimaryTableName” | Required. The table that provides the join information for grouping the data on the target table. Must be a table that is linked to the target table. If the link [transactions].[cid] → [customer].[cid] exists, and [customer] is specified as the key table, data will be grouped by [cid] when calculating DistinctByKey. |
| **D****istinct Key** | “p2”:"DistinctKeyName" | Required. The Field on the target table used to determine if a unique value has been found Within the key group, the first time a value is encountered it is flagged as 1, all other times it is flagged as 0. |

## JSON Sample

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

## Usage Notes

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

See Also:

- Engineering | Expression Field

## Example

| Example | Details |
| --- | --- |
| **Description** | **Flag Each unique instance of product-date-ns-2020, grouped by customer** |
| **Input** | - Table: = transactions - Filter:= [No Filter] - **Function: = DistinctByKey** - Key Table: = customer - Distinct Key:=[transactions].[product-date-ns-2020] - Name = distinct_pr-date-ns-2020 |
| **Sample** | ![](https://cdn.document360.io/73b6469b-c1e4-47e9-aa65-986c8ebd17ca/Images/Documentation/Gen_DistinctByKey_Example.png) |