SQL Duplicate Values After Transformation

EasySQL · PostgreSQL00:00

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Your question is SQL Duplicate Values After Transformation. Start with the requirements and the one table on the right.

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Problem

Apex Systems QA engineers are validating imported contact records. Some email addresses differ only by capitalization or accidental surrounding spaces, which can create duplicate accounts in an internal QA data set.

Write a PostgreSQL query to identify duplicate email values after applying the transformation LOWER(TRIM(external_email)).

Requirements

Normalize each email by trimming surrounding whitespace and converting it to lowercase.
Return only non-empty normalized values that occur more than once.
Return the normalized email and its duplicate count, ordered alphabetically by the normalized email.

Schema

contact_imports

Column	Type	Description
import_idPK	INT	Unique imported record identifier
external_email	VARCHAR(255)	Email value received from an external source

Tablescontact_imports

Your solutionPostgreSQL

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