Ensuring Excel Data Accuracy | Dataford Interview Questions

How do you ensure accuracy when managing large, complex data sets in Excel?

Write a PostgreSQL query that audits imported records against reference records and returns every discrepancy, including records present in only one source. Treat two NULL values as matching.

Output

One row per discrepancy, with record_key, imported and expected amounts, imported and expected statuses, and discrepancy_type.
Exclude records whose values and statuses match.
Order by record_key ascending.

Schema

excel_imports

Column	Type	Description
import_idPK	INT	Unique identifier for the imported row
record_key	VARCHAR(20)	Business key identifying the record
imported_amount	DECIMAL(12,2)	Amount loaded from the imported data
imported_status	VARCHAR(20)	Status loaded from the imported data

reference_records

Column	Type	Description
reference_idPK	INT	Unique identifier for the reference row
record_key	VARCHAR(20)	Business key identifying the record
expected_amount	DECIMAL(12,2)	Authoritative amount for comparison
expected_status	VARCHAR(20)	Authoritative status for comparison

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Problem