[TIL] How to query all users that have the same first name in Postgres

A SQL query to list all users with duplicated first names can be useful in a variety of scenarios, including:

Overall, the goal of this query is to help you ensure the quality and accuracy of your data, and to help you make informed decisions about how to manage that data.

Here's an example SQL query for PostgreSQL that will list all users that have duplicated first names:

sql 
Copy code
WITH cte AS (
  SELECT first_name, count(*)
  FROM users
  GROUP BY first_name
  HAVING count(*) > 1
)
SELECT u.*
FROM users u
JOIN cte ON u.first_name = cte.first_name

The guide demonstrates how to use a SQL query to identify duplicate first names in a table of users by utilizing the GROUP BY and HAVING clauses. The query groups the rows in the table by the first name column and uses the HAVING clause to specify that the count of first names must be greater than one in order to be considered a duplicate. The query returns a list of all first names that appear more than once in the table, along with the number of times each name appears.

This article can be useful for individuals who work with databases and need to find and analyze data in a table of users in a PostgreSQL database. The SQL query provided in the article can be adapted for use in similar situations and can help users quickly identify duplicates in their data.