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# Deleting Selected Records from Delta Tables

In this lesson, we will learn how to delete selected records from a Delta table in Databricks Unity Catalog using SQL. The operation we will focus on is deleting a record based on a specific condition.

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## Overview

Delta tables in Databricks provide a robust and scalable way to manage structured data. One of the essential operations when working with Delta tables is the ability to delete specific records. This is commonly done using the `DELETE FROM` statement in SQL.

In this lesson, we will execute the following SQL command to delete a record from the `training.sales.customers` table where the `customer_id` is equal to 2:

“`sql
DELETE FROM training.sales.customers WHERE customer_id = 2;
“`

Before proceeding, it is important to understand that deletions from Delta tables are irreversible and should be performed with caution. Always verify the data before deletion.

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## Step-by-Step Execution

### Step 1: Verify the Data

Before deleting any records, it is a good practice to verify the data that will be affected. You can do this by running a `SELECT` query to view the record you plan to delete:

“`sql
SELECT * FROM training.sales.customers;
“`

This will display all the records in the `customers` table, allowing you to confirm the `customer_id` and other details of the record you want to delete.

### Step 2: Delete the Selected Record

Once you are confident that you want to delete the record with `customer_id = 2`, execute the following SQL command:

“`sql
DELETE FROM training.sales.customers WHERE customer_id = 2;
“`

This statement will permanently remove the record from the table.

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## Important Notes

– **Irreversibility**: Once a record is deleted from a Delta table, it cannot be recovered unless you have a backup or a version history enabled.
– **Permissions**: Ensure that the user executing the `DELETE` operation has the appropriate permissions to modify the table.
– **Delta Table Properties**: Delta tables support ACID transactions and versioning, so deletions are atomic and consistent within the table.

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## Conclusion

In this lesson, you have learned how to delete selected records from a Delta table in Databricks Unity Catalog using SQL. You practiced verifying the data with a `SELECT` query and then executed the `DELETE` operation to remove a specific record.

Remember to always double-check your data before performing deletions, and consider using versioning or backups to safeguard against accidental data loss.