You want to calculate the total sales per customer and then find customers with sales over 1000. Which approach using CTEs is best?

hard📝 Application Q8 of 15

PostgreSQL - Common Table Expressions

AUse a CTE to sum sales per customer, then filter in the main query

BWrite a single query without CTEs using nested subqueries

CCreate a temporary table instead of a CTE

DUse multiple CTEs without filtering

Step-by-Step Solution

Solution:

Step 1: Understand the problem requirements
You need to aggregate sales per customer and then filter those with totals over 1000.
Step 2: Evaluate CTE usage for clarity and efficiency
Using a CTE to calculate sums first, then filtering in the main query, makes the query clear and maintainable.
Final Answer:
Use a CTE to sum sales per customer, then filter in the main query -> Option A
Quick Check:
CTEs help separate aggregation and filtering = A [OK]

Quick Trick: Use CTEs to separate calculation and filtering steps [OK]

Common Mistakes:

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