Improve Query Performance by Selecting Only Required Columns

Avoiding SELECT * for Better Performance

Write a SQL query to retrieve only specific columns instead of using SELECT.

Solution:

-- Retrieve only the required columns from the Employees table.
SELECT EmployeeID, Name, Department
FROM Employees;

Explanation:

• Purpose of the Query :
• The goal is to improve query performance by selecting only the necessary columns.
• Key Components :
• SELECT EmployeeID, Name, Department: Specifies only the required columns.
• Avoids retrieving all columns with SELECT *.
• Why avoid SELECT *?:
• Retrieving unnecessary columns increases I/O overhead and memory usage.
• It also prevents potential issues with schema changes.
• Real-World Application :
• In web applications, retrieving only the required data reduces latency and improves user experience.

Notes:

• Always specify the exact columns needed for a query.
• Use tools like query profilers to measure the impact of SELECT *.
• Important Considerations:
• Ensure that the selected columns include all required data.

For more Practice: Solve these Related Problems:

• Write a SQL query to retrieve only the product ID and name from the Products table, avoiding the use of SELECT *.
• Write a SQL query to fetch only the customer ID and email from the Customers table without using SELECT *.
• Write a SQL query to display only the employee ID and department from the Employees table, avoiding unnecessary columns.
• Write a SQL query to retrieve only the order ID and order date from the Orders table without selecting all columns.

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