Repeated Email Detector

Easy

You are given a table named Person that stores account records: id: unique identifier for each row email: lowercase email string (never null) Your task is to produce a result set containing only the email addresses that occur more than once in the table. Requirements: Return each repeated email exactly once Output must contain a single column named email Result row order can be arbitrary This problem should be solved in both: SQL (SQLite 3.27.2) Pandas

Example 1

Input

Person:
| id | email               |
|----|---------------------|
| 1  | alex@site.com       |
| 2  | beta@site.com       |
| 3  | alex@site.com       |

Output

[
  {"email":"alex@site.com"}
]

Explanation

alex@site.com appears twice, so it is included once in the output.

Example 2

Input

Person:
| id | email                 |
|----|-----------------------|
| 1  | sam@org.io            |
| 2  | eva@org.io            |
| 3  | sam@org.io            |
| 4  | eva@org.io            |
| 5  | lee@org.io            |

Output

[
  {"email":"eva@org.io"},
  {"email":"sam@org.io"}
]

Explanation

Both eva@org.io and sam@org.io have frequency 2. lee@org.io appears once and is excluded.

Example 3

Input

Person:
| id | email                 |
|----|-----------------------|
| 10 | one@mono.net          |
| 11 | two@mono.net          |
| 12 | three@mono.net        |

Output

[]

Explanation

No email is repeated, so the result is empty.

Constraints

1 <= number of rows in Person <= 10,000
Person.id is unique
Person.email is non-null and lowercase
Output must contain exactly one column named email
Use SQLite 3.27.2 semantics for SQL submissions
For Pandas submissions, return a DataFrame with one column: email

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