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SQL Program 36: Find duplicate student names

Praveen KulkarniPraveen Kulkarni

SQL learning illustration

CS TECHIIE | SQL Notes and Solutions

Practical SQL exercise: Shows names appearing more than once.

Objective

Shows names appearing more than once.

Explanation

Read the statement clause by clause and predict the result before executing it. These examples use common relational SQL; table setup and exact syntax can vary between MySQL, PostgreSQL, SQL Server, Oracle and SQLite.

Safety check

Before running UPDATE or DELETE, run a SELECT with the same WHERE condition. Use a test database and a transaction for changes you need to verify.

Program / SQL Solution

SELECT name,COUNT(*) AS occurrences FROM students GROUP BY name HAVING COUNT(*)>1;

Practice and revision

  • Run the example and verify the output.
  • Change the input and test normal, boundary and invalid cases.
  • Write the solution again without looking at the notes.

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