Ensuring Data Quality with Large Oracle Databases

Explain how you ensure data accuracy and quality when working with large Oracle databases.

For this hands-on SQL exercise, use the provided PostgreSQL tables to flag transaction-level quality issues. Check invalid amounts, missing or blank references, duplicate references, and missing account or customer relationships.

Output

One row per transaction with the columns transaction_id, transaction_reference, account_id, customer_name, amount, issue_count, and quality_status.
Include all transactions, label rows with one or more issues as ISSUE, and label clean rows as VALID.
Order by issue_count descending, then transaction_id ascending.

Schema

customers

Column	Type	Description
customer_idPK	INT	Unique customer identifier
customer_name	VARCHAR(100)	Customer display name
region	VARCHAR(50)	Customer geographic region

accounts

Column	Type	Description
account_idPK	INT	Unique account identifier
customer_id	INT	Customer associated with the account
account_status	VARCHAR(20)	Current account status

transactions

Column	Type	Description
transaction_idPK	INT	Unique transaction identifier
transaction_reference	VARCHAR(30)	Source-system transaction reference
account_id	INT	Account associated with the transaction
amount	NUMERIC(12,2)	Transaction amount

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