Understanding Derived Table Query Performance with EXPLAIN in MySQL

Analyze Derived Table Query Performance with EXPLAIN

Write a MySQL query that uses EXPLAIN to analyze the performance of a query utilizing a derived table to calculate total orders per customer and then filters for customers with more than 5 orders.

Solution:

-- Use EXPLAIN to analyze the performance of a query using a derived table.
EXPLAIN
SELECT dt.CustomerID, dt.OrderCount
FROM (
    SELECT CustomerID, COUNT(*) AS OrderCount
    FROM Orders
    GROUP BY CustomerID
) AS dt
WHERE dt.OrderCount > 5;

Explanation:

• Purpose of the Query:
• To evaluate the execution plan of a query that uses a derived table for aggregation.
• Helps identify potential performance issues when subqueries are used as temporary tables.
• Key Components:
• Derived Table: Computes the count of orders per CustomerID.
• WHERE dt.OrderCount > 5 : Filters for customers with a high volume of orders.
• Real-World Application:
• Useful for customer segmentation or identifying high-value customers based on order volume.

Notes:

• Derived tables are processed as temporary tables; ensure they are optimized with proper indexing if needed.
• Use EXPLAIN to verify that the derived table approach meets performance requirements.

For more Practice: Solve these Related Problems:

• Write a MySQL query that uses EXPLAIN to analyze the performance of a query utilizing a derived table to calculate total sales per product and then filters for products with more than 100 sales.
• Write a MySQL query that uses EXPLAIN to analyze the performance of a query utilizing a derived table to calculate total projects per department and then filters for departments with more than 10 projects.
• Write a MySQL query that uses EXPLAIN to analyze the performance of a query utilizing a derived table to calculate total orders per customer and then filters for customers with more than 20 orders.

Have another way to solve this solution? Contribute your code (and comments) through Disqus.

Previous MySQL Exercise: Optimize Query with Generated Column and Index.