---
title: "LogChanges"
slug: "logchanges-1"
updated: 2023-09-18T15:17:07Z
published: 2023-09-18T15:17:07Z
canonical: "docs.datajet.app/logchanges-1"
---

> ## 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.

# LogChanges

Compares and Logs summary changes between the values of 2 fields.

| Key | Value(s) | Description |
| --- | --- | --- |
| method | "LogChanges" | Logs summary changes between the values of 2 fields. |
| fromField | "InputFieldName" | Required. Input Field Name. Must be discrete. |
| toField | "OutputFieldName" | Required. Output Field Name. Must be discrete. |
| project | "CurrentProjectName" | Current Project Name |

Use this method to obtain summary data about changes in values.

```json
{
  "method": "StartErrorLog",
  "filename": "ScriptLog_%DSTAMP%",
  "mailTo": [
    "me@email.com"
  ],
  "project": "Test1"
}

{
  "method": "LogChanges",
  "fromField": "customer.gender-code",
  "toField": "customer.gender",
  "project": "Test1"
}
```

![](https://cdn.document360.io/73b6469b-c1e4-47e9-aa65-986c8ebd17ca/Images/Documentation/image-1695050148333.png)

- LogChanges can only be called on [Discrete Fields](/v1/docs/getting-started-data-types).
- To view the output from LogChanges, see the Log tab in [Script Editor](/v1/docs/script-editor).
- To capture output from LogChanges in a more persistent format, set up Script Logging using [StartErrorLog](/v1/docs/starterrorlog).
- A more systematic form of LogChanges can be achieved using [ETLSummaryFromTable](/v1/docs/etlsummaryfromtable) or [ETLSummaryFromTableEx](/v1/docs/etlsummaryfromtableex)

Example Output

```custom
LogChanges customer.occupation -> customer.modified-occupation

Rows Processed : 14
Rows Changed : 4
Rows Kept : 10

"junior programmer" -> "junior coder" : 1,262,462
"lead programmer" -> "lead coder" : 561,282
"programmer" -> "coder" : 2,735,469
"senior programmer" -> "senior coder" : 1,750,315
```

See [Replace Function](/v1/docs/replace-function) for example use.