> For the complete documentation index, see [llms.txt](https://docs.langstack.com/welcome/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.langstack.com/welcome/get-started/learn-langstack/introduction-to-etl-pipeline/exercise-1-skip-customer-records.md).

# Exercise 1: Skip Customer records

A Data Source contains Customer IDs ranging from 1 to 17 (in odd numbers). The user wants to skip some records from being written to the destination. In this exercise, skip the records with Customer\_IDs as 3, 5, and 7.

## Requirements

* Read customer information from a CSV source and write to the target entity “(UserName)\_Acc\_skipCustomers” having the following fields:
  * Field name: Customer\_ID, data type: string
  * Field name: Join\_Date, data type: DateTime 

<figure><img src="https://media.langstack.com/documentation/media/images/code/training_manual/chapter_9/ch9ex1skipcustentity.png" alt=""><figcaption></figcaption></figure>

* The stored records should have the month updated in the join date as “3”.&#x20;
* Users should be able to skip records based on Customer\_ID.&#x20;
* The skipped records detail is updated in another entity.

## Solution

* Read data from source and map source fields to destination.&#x20;
* In the “On Reading record” function, define actions to skip records if they match values in StartupParameters.&#x20;
* In the “On Skipped record” function, define actions to make a list of deleted records.&#x20;
* In the “On Completed” function, define actions to create records from the list containing details of the skipped records in a target entity.