View Cost Estimates for Query Execution

Estimating Query Costs with EXPLAIN in PostgreSQL

Write a PostgreSQL query to display the estimated costs for executing a SELECT query with filtering conditions using EXPLAIN.

Solution:

-- Specify the action to show the estimated execution plan and cost.
EXPLAIN  
-- Define the query to retrieve all columns from the Employees table.
SELECT * FROM Employees  
-- Add a condition to filter rows where salary is greater than 50000.
WHERE salary > 50000; 

Explanation:

• Purpose of the Query:
• To view the cost estimates that PostgreSQL assigns to a query with a WHERE clause.
• This aids in understanding how different filter conditions impact performance.
• Key Components:
• salary > 50000 : The filtering condition affecting query performance.
• EXPLAIN : Provides cost estimates such as startup cost and total cost.
• Real-World Application:
• Helps in deciding whether additional indexes or query rewriting is needed for performance improvements.

Notes:

• Estimated costs are influenced by table statistics and may differ from actual runtimes.

For more Practice: Solve these Related Problems:

• Write a PostgreSQL query using EXPLAIN to display estimated costs for a SELECT query with a WHERE clause filtering on a date column in the "Events" table.
• Write a PostgreSQL query using EXPLAIN to show cost estimates for a SELECT query that sorts data on the "price" column in the "Items" table.
• Write a PostgreSQL query using EXPLAIN to display cost estimates for a SELECT query with multiple conditions in the "Orders" table.
• Write a PostgreSQL query using EXPLAIN to analyze a SELECT query that includes an aggregate function on the "Sales" table grouped by "region".

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