Explain what it means to have duplicate records in a database table.

The presence of duplicate records in a database table means that there are two or more rows in the table with matching values in one or more columns that should be unique logically.

This can lead to:

• Incorrect data and application errors.
• Data integrity issues.
• Complications in data processing and analysis.

Reasons for duplicates:

• Lack of uniqueness constraints (UNIQUE) at the database level.
• Application logic errors during data insertion.
• Concurrent operations without proper synchronization.

To detect duplicates, you can use an SQL query with grouping, for example:

SELECT column1, column2, COUNT(*)
FROM table_name
GROUP BY column1, column2
HAVING COUNT(*) > 1;

To prevent duplicates, you should add unique constraints and handle data insertion correctly in the application.