Complete Data Persistence Bootcamp Practice Test 2026 | Exam

In a relational database with a high volume of concurrent transactions, which isolation level prevents dirty reads, non-repeatable reads, and phantom reads, but may significantly impact performance due to locking?

You are designing a schema for an e-commerce application. The "Orders" table has a foreign key "customer_id" referencing the "Customers" table. Which referential action should be specified on the foreign key to automatically set the "customer_id" to NULL in all of a customer's orders if that customer record is deleted?

A database administrator notices that a frequently executed query, which joins four large tables, is performing full table scans. Which of the following is the MOST targeted and effective action to improve its performance without changing the query logic?