Why am i getting the 'error: duplicate key value violates unique constraint'?

This error occurs when you try to insert or update a record that would lead to a duplicate value in a column with a unique constraint.

Example:

ERROR:  duplicate key value violates unique constraint "users_pkey"

Solution:

1. Make sure you're not inserting a duplicate value.
2. Identify the constraint causing the issue.
3. Modify your data or query to respect the uniqueness constraint.