---
title: "CreateKeyTable"
slug: "createkeytable"
updated: 2023-05-16T10:22:45Z
published: 2023-05-16T10:22:46Z
canonical: "docs.datajet.app/createkeytable"
---

> ## 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.

# CreateKeyTable

Creates a new table from the unique values of the specified field

Use this method to create a resolution table for analysis or to reduce the number of records passed into engineering functions.

### Method

| Key | Value(s) | Description |
| --- | --- | --- |
| method | "CreateKeyTable" | Creates a table with one row for each unique value in provided key field. |
| project | "CurrentProject" | The active project. |
| key | "TableName.FieldName" | Fully qualified key field. The maximum number of discrete values in the key field is dependant on available memory. A well-resourced server should support keys of ~ 20 million discrete values. The underlying constraint is whether or not there is sufficient resource to do a FirstDiscrete on the field in question. See FirstDiscrete for details on limitations with this function. |
| targetTable |  | The name of the key table to create |
| join | true/false | If true, the newly created key table will be joined to the source table. |

### Usage

Modelling and PluginsThe CreateKeyTable technique is often used to reduce the size of a problem set.    To see examples of this, open Script Editor, select a new script, and then choose one of the following Plugins:

- Alt Double Metaphone
- Fuzzy Double Metaphone
- Fuzzy NYSIIS

CreateKeyTable takes every unique value in Source Table for the specified key, and uses it to make a fully unique key in a new Key Table. The Key Table then becomes the primary table in the join.

![](https://cdn.document360.io/73b6469b-c1e4-47e9-aa65-986c8ebd17ca/Images/Documentation/image-1684232356487.png)

### Example

```json
{
  "method": "CreateKeyTable",
  "project": "CurrentProject",
  "key": "Table.FieldName",
  "targetTable": "NameOfNewTable",
  "join": false
}
```

## Related

- [Make Key Table](/make-key-table.md)
- [FirstDiscrete](/firstdiscrete.md)