LeetCode SQL Practice | Dataford Interview Questions

Business Context

KPIT's Connected Engineering portal receives email addresses from employees and external collaborators. Different address formats can refer to the same mailbox, so reporting must count each valid destination only once.

Task

Write a PostgreSQL query that calculates the number of unique normalized email addresses in portal_emails.

Requirements

Remove every period from the local part before the @ symbol.
Ignore the plus suffix in the local part, including the + character and everything after it.
Count each normalized email address once and exclude rows where email is NULL.

Schema

portal_emails

Column	Type	Description
email_idPK	INT	Unique identifier for the submitted email row
email	VARCHAR(255)	Submitted email address

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Problem