Optimizing Subqueries in MySQL with EXPLAIN

Last update on October 17 2025 12:44:21 (UTC/GMT +8 hours)

Analyze Subquery Performance with EXPLAIN

Write a MySQL query that uses EXPLAIN to analyze the performance of a query with a subquery that retrieves orders for customers from Berlin.

Solution:

-- Use EXPLAIN to analyze a query with a subquery filtering orders for customers from Berlin.
EXPLAIN SELECT * FROM Orders
WHERE CustomerID IN (
    SELECT CustomerID FROM Customers WHERE City = 'Berlin'
);

Explanation:

Purpose of the Query:

To analyze the execution plan of a query that includes a subquery.
Helps in identifying potential inefficiencies in subquery execution.

Key Components:

EXPLAIN : Initiates the performance analysis.
IN (SELECT CustomerID FROM Customers WHERE City = 'Berlin') : The subquery filters customers based on their city.

Real-World Application:

Useful for optimizing queries that retrieve data based on relationships between tables with subqueries.

Notes:

Consider rewriting subqueries as JOINs if performance issues are detected.
Use EXPLAIN to compare the performance of different query structures.

For more Practice: Solve these Related Problems:

Write a MySQL query to use EXPLAIN to analyze the performance of a query with a subquery that retrieves employees from departments with more than 10 members.
Write a MySQL query to use EXPLAIN to analyze the performance of a query with a subquery that retrieves products with prices higher than the average price.
Write a MySQL query to use EXPLAIN to analyze the performance of a query with a subquery that retrieves orders placed by customers who have made more than 5 purchases.
Write a MySQL query to use EXPLAIN to analyze the performance of a query with a subquery that retrieves users who belong to roles with administrative privileges.

Go to:

PREV : Force Index usage in a Query.
NEXT : Utilize Covering Index for Query Optimization.

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