Understanding Transactions and SQL Queries | Dataford Interview Questions

What is transaction, write few sql queries

Asked in the Round 2 - Technical stage. Write PostgreSQL statements that demonstrate an atomic account transfer, recording the transfer only when the debit and credit succeed.

Output

One row for transfer 2001
Columns: transfer_id, sender_name, recipient_name, amount, sender_balance, recipient_balance
Show the balances after the transfer and order by transfer_id ascending

Schema

accounts

Column	Type	Description
account_idPK	INT	Unique account identifier
account_name	VARCHAR(100)	Account holder name
balance	NUMERIC(12,2)	Current account balance

transfers

Column	Type	Description
transfer_idPK	INT	Unique transfer identifier
from_account_id	INT	Account sending the funds
to_account_id	INT	Account receiving the funds
amount	NUMERIC(12,2)	Transferred amount
transferred_at	DATE	Transfer date
memo	VARCHAR(200)	Optional transfer note

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