SQL
Identifying Duplicate Rows in a SQL Table
Learn to find and list all duplicate rows in a SQL table based on one or more columns using GROUP BY and HAVING COUNT > 1 clause.
SELECT email, COUNT(*) AS num_duplicates
FROM users
GROUP BY email
HAVING COUNT(*) > 1;
How it works: This query identifies duplicate records within the `users` table based on the `email` column. It groups all rows by their `email` and then uses the `HAVING` clause to filter for groups where the count of rows is greater than 1, indicating that the email address appears multiple times. This is crucial for data cleaning and ensuring data integrity.