Assume we want to retrieve only the account numbers that have performed at least one transaction.

In this task, we have a query that is not optimized. Your task is to rewrite it in a more optimal way.

Here is a list of the main query rewriting techniques to enhance optimization:

1. Explicitly Specify Columns: instead of using the asterisk (*) wildcard, explicitly mention column names in queries for better performance, readability, and maintainability;

2. Minimize Subqueries: reduce the use of subqueries to optimize query performance. Consider alternatives like joins or derived tables to avoid complexity and overhead;

3. Avoid Repeated IN Operators: limit the use of the IN operator in queries to prevent performance impact. Instead, consider using JOIN or EXISTS clauses for more efficient execution plans;

4. Organize Joins Logically: start SQL joins with the main table and then join with related tables to optimize query organization and database engine optimization;

5. Use Restrictive WHERE Conditions: improve query performance by including restrictive conditions in the WHERE clause to filter rows and enhance execution speed;

6. Refactor Code into Stored Procedures or Functions: encapsulate repetitive code segments into stored procedures or user-defined functions for code reusability, modularity, and easier maintenance. These can reduce redundancy and optimize SQL queries.