Handle Missing Values and Outliers | Dataford Interview Questions

How would you handle missing values or outliers in a large-scale transaction dataset?

For this SQL exercise, identify transaction records with missing values or unusually large or small amounts relative to other transactions from the same store. Use the supplied data and return only records requiring review.

Output

One row per flagged transaction with transaction_id, store_name, amount, and issue_type
Include missing amounts, missing customer IDs, and amounts outside the store-level 1.5 IQR fences
Sort by transaction_id ascending

Schema

transactions

Column	Type	Description
transaction_idPK	INT	Unique transaction identifier
store_id	INT	Store associated with the transaction
customer_id	INT	Customer associated with the transaction
amount	DECIMAL(12,2)	Transaction amount

stores

Column	Type	Description
store_idPK	INT	Unique store identifier
store_name	VARCHAR(100)	Store display name

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Problem