Deleting Data from Values in another Table

Scenario Description:

1. `Customers`: This is the parent table, containing customer information.
   • Columns: CustomerID, CustomerName, AccountStatus
2. `Orders`: This is the child table, containing orders placed by customers.
   • Columns: OrderID, CustomerID, OrderDate, OrderAmount

SQL Statement to Achieve the Requirement:

SELECT c.CustomerID, o.OrderID, o.OrderDate, o.OrderAmount
FROM Orders o
JOIN Customers c ON o.CustomerID = c.CustomerID
WHERE c.AccountStatus = 'Inactive';

DELETE FROM Orders
WHERE CustomerID IN (
    SELECT CustomerID
    FROM Customers
    WHERE AccountStatus = 'Inactive'
);

• Step 1: Before executing the DELETE statement, it is crucial to review the data to ensure that the correct records are being targeted. A SELECT statement is used to retrieve and display orders associated with inactive customers. This step helps in verifying that the subsequent DELETE operation will affect the intended records.
• Step 2: The DELETE statement is executed on the 'Orders' table. The WHERE clause specifies that only orders belonging to inactive customers should be deleted. This is determined by a subquery, which retrieves the CustomerID values from the 'Customers' table where the 'AccountStatus' is 'Inactive'.

Important Considerations:

• Data Verification: Always verify the data before executing a DELETE statement, especially when dealing with related tables. This helps in preventing accidental deletion of unintended records.
• Transaction Control: Consider wrapping the DELETE statement within a transaction, providing the ability to rollback changes if something goes wrong.
• Backup: Ensure that there are recent backups of the data, or consider taking a backup before executing the DELETE statement, to provide a restore point in case of any issues.
• Referential Integrity: Make sure that referential integrity constraints, such as foreign keys, are appropriately configured to maintain data consistency.