SQL: Top N Duplicate Groups | Dataford Interview Questions

Write a SQL query to identify the top N duplicate groups by count in a table.

For this exercise, use market_data_records and set N to 3. A duplicate group contains identical values across instrument_symbol, event_date, price, and quantity.

Output

One row per duplicate group, with instrument_symbol, event_date, price, quantity, and duplicate_count.
Include only groups occurring more than once.
Return the three groups with the highest counts, ordered by duplicate_count descending, then the grouping columns ascending with NULL values last.

Schema

market_data_records

Column	Type	Description
record_idPK	INT	Unique market data record identifier
instrument_symbol	VARCHAR(12)	Instrument symbol
event_date	DATE	Date associated with the market data event
price	NUMERIC(12,2)	Recorded instrument price
quantity	INT	Recorded contract quantity

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