You have a query with four nested subqueries that is hard to read. How would you restructure it?

I would replace the nested subqueries with Common Table Expressions (CTEs) or temporary tables. Each subquery becomes a named CTE that performs a single logical step. The main query then references these CTEs, making the flow easier to read. For example, instead of SELECT ... FROM (SELECT ... FROM (SELECT ...)) AS a, I would write WITH cte1 AS (SELECT ...), cte2 AS (SELECT ... FROM cte1), cte3 AS (SELECT ... FROM cte2) SELECT ... FROM cte3. This linearizes the logic, improves maintainability, and often allows the optimizer to better understand the query structure.