---
title: "Count"
slug: "count"
updated: 2023-09-20T17:47:16Z
published: 2023-09-20T17:47:16Z
canonical: "docs.datajet.app/count"
---

> ## 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.

# JoinLayers

## General: JoinLayers

#### Join Analysis Functions

## Purpose

Use these functions to:

- Count the number of layers that matched for each record in a join
- Find the first layer that matched for a record
- Obtain the binary value of matching layers
- Get a match score for each record

## Return Value

| Property | Value |
| --- | --- |
| **FieldType** | Integer |
| **FieldSize** | Low |
| **DataType** | Discrete |
| **DataSize** | Short / Integer / LongInteger / Double |

```shell
Example Return Value:
```

![](https://cdn.document360.io/73b6469b-c1e4-47e9-aa65-986c8ebd17ca/Images/Documentation/image-1695230457196.png)

## Parameters

| Parameter | JSON | Description |
| --- | --- | --- |
| **Table** | “targetTable”: “foreigntablename” | Required. The foreign table in the join. |
| **Filter** | “dataset”: {DataSet_JSON} | Optional. If a filter is applied, records not in the filter recordset will be returned as null. |
| **Function** | "function":"joinlayers" | "joinlayers" |
| Primary Table | “p1”: “primarytablename” | Required. The primary table in the join. |
| Function | “p2”: "function" | Required. One of: - Count - Counts number of layers matched for each record. - First - Returns the first layer matched for each record. - Score - Total score, higher values for earlier (better) matches. - Raw - Binary value of matching layers (1st layer = bit 0) |

## JSON Sample

```json
{
  "method": "BuildBakedField",
  "targetTable": "DATA_DS1",
  "overwrite": true,
  "name": "dj_JL_Count_DS1",
  "function": "joinlayers",
  "p1": "customers",
  "p2": "Count",
  "project": "SharedLibrary"
}
```

## Usage Notes

First build the join, using [AddJoin](/v1/docs/addjoin) and [AddJoinLayer](/v1/docs/addjoinlayer). Then create JoinLayer fields.

At least one join layer must be present for JoinLayer functions to be calculated.

See Also:

- Engineering | [Expression](/v1/docs/expression-field) Field
- [Joins](/v1/docs/joins)

## Example

| Example | Details |
| --- | --- |
| **Description** | Count join layers for each record in customer/transaction join |
| **Input** | - Table: = "transactions" - Filter: = [No Filter] - **Function: = "joinlayers"** - p1:= "customers" - p2:= "count" - Name: = dj_JL_Count |