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Optimize Slow Queries on Large Data
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Optimize Slow Queries on Large Data

MediumSQL · PostgreSQL

Problem

How do you optimize a query that is performing poorly on a large dataset in Citi environments?

You are given a query that returns slow results on a large transactional dataset. Improve it so it returns the same answer with better performance.

Output

  1. Return the same result set as the original query
  2. Keep the output columns and row order unchanged
  3. Do not change the business logic or remove any required rows

Schema

transactions
ColumnTypeDescription
transaction_idPKBIGINTUnique transaction identifier
account_idBIGINTAccount associated with the transaction
transaction_dateDATEDate the transaction was posted
amountNUMERIC(12,2)Transaction amount
statusVARCHAR(20)Transaction status
accounts
ColumnTypeDescription
account_idPKBIGINTUnique account identifier
region_nameVARCHAR(50)Account region
is_activeBOOLEANWhether the account is active
Tablestransactionsaccounts
Interviewer

Your question is Optimize Slow Queries on Large Data. Start with the requirements and the two tables in the Question tab.

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