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Detect and Resolve Duplicate Transactions
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Detect and Resolve Duplicate Transactions

MediumSQL · PostgreSQL

Problem

Write a SQL query to find duplicate records in a transaction table and explain how you would resolve them at Zions Bancorporation.

Treat transactions with the same account, date, amount, type, and reference number as duplicates. Return only the records that should be reviewed for quarantine or removal, retaining the lowest transaction ID as the canonical record.

Output

  1. One row per non-canonical duplicate transaction
  2. Columns: transaction_id, account_id, transaction_date, amount, transaction_type, reference_number, duplicate_count, and duplicate_rank
  3. Order by account_id, transaction_date, and transaction_id

Schema

transactions
ColumnTypeDescription
transaction_idPKBIGINTUnique transaction identifier
account_idVARCHAR(20)Bank account identifier
transaction_dateDATEBusiness date of the transaction
amountNUMERIC(12,2)Transaction amount
transaction_typeVARCHAR(20)Transaction classification
reference_numberVARCHAR(30)External transaction reference
statusVARCHAR(20)Processing status
Tablestransactions
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