Identify Duplicate Records Based on Columns

SELECT
  email, first_name, last_name,
  COUNT(*) AS num_duplicates
FROM
  users
GROUP BY
  email, first_name, last_name
HAVING
  COUNT(*) > 1;

How it works: This SQL query is highly useful for data cleaning and ensuring data integrity by identifying duplicate records. It groups rows by a combination of columns (e.g., `email`, `first_name`, `last_name`) that are expected to be unique. The `HAVING COUNT(*) > 1` clause then filters these groups to show only those combinations that appear more than once, effectively listing all the duplicate entries along with their count. This helps in pinpointing and resolving redundant data in your database.