Evaluate Query Plans using EXPLAIN for Optimization

Analyzing Query Performance with EXPLAIN

Write a PostgreSQL query to use the EXPLAIN statement to analyze how indexes are used in query planning.

Solution:

-- Specify the action to analyze the query plan.
EXPLAIN 
-- Define the query to be analyzed.
SELECT * FROM Employees 
-- Add the condition for filtering rows in the query.
WHERE last_name = 'Smith';

Explanation:

• Purpose of the Query:
• To display the query execution plan and understand whether the index is being used.
• Key Components:
• EXPLAIN : Command that shows the query plan without executing the query.
• SELECT * FROM Employees WHERE last_name = 'Smith' : The query under analysis.

Notes:

• Review the output to verify if an index scan is utilized.
• This process helps in fine-tuning and troubleshooting query performance issues.

For more Practice: Solve these Related Problems:

• Write a PostgreSQL query to analyze the execution plan for a query filtering by "zipcode" in the "Addresses" table using EXPLAIN.
• Write a PostgreSQL query to analyze the execution plan for a join between the "Employees" and "Departments" tables using EXPLAIN.
• Write a PostgreSQL query to analyze the execution plan for a query using the expression index on LOWER(username) in the "Users" table with EXPLAIN.
• Write a PostgreSQL query to analyze the execution plan for a multi-condition query in the "Orders" table using EXPLAIN.

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