Find First Recurring Element

MediumSQL · PostgreSQL

Problem

Given an array of integers, write a function to find the first recurring element.

For this SQL version, the array is stored as one row per element in integer_sequence. Return the recurring value whose first appearance has the smallest position. Ignore NULL values.

Output

One row containing recurring_value and first_position.
Return the recurring value with the earliest first appearance.
Return no rows if no non-NULL value recurs.

Schema

integer_sequence

Column	Type	Description
positionPK	INT	One-based position of the integer in the sequence
integer_value	INT	Integer stored at the sequence position

Tablesinteger_sequence

CodePostgreSQL

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