Database Interaction GPYC Practice Questions (Page 2)

Questions 6–10

1. 6application · medium

   A Python script processes a batch of INSERT statements into a PostgreSQL database. The script should commit the transaction only if all inserts succeed; otherwise, it should roll back. Which control flow correctly implements this?

   • AWrap all inserts in a try block, call commit() at the end of the try, and call rollback() in the except block.
   • BCall commit() after each individual insert and rely on the database to skip failed ones.
   • CDo not use transactions; let the database autocommit each insert.
   • DCall rollback() before each insert and commit() only if the last insert succeeds.
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2. 7application · medium

   A Python script transfers funds between two bank accounts in a PostgreSQL database. It debits the source account, then credits the destination account. If the credit fails, the script must ensure the debit is not permanently saved. What is the correct approach?

   • ACall connection.rollback() before the debit and connection.commit() after the credit.
   • BPerform both operations, then call connection.commit() only if both succeed; otherwise call connection.rollback().
   • CCall connection.commit() after the debit and again after the credit.
   • DUse autocommit mode so each statement is saved immediately.
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4. 8foundation · easy

   After executing a SELECT query, what does the cursor.fetchall() method return?

   • AA single tuple representing the first row
   • BA list of tuples representing all remaining rows
   • CA dictionary containing column names and values
   • DAn integer representing the number of rows
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5. 9foundation · easy

   What is the purpose of calling connection.rollback() in a database transaction?

   • ATo undo all changes made since the last commit
   • BTo close the database connection
   • CTo re-execute the last query
   • DTo save changes to the database
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6. 10foundation · easy

   Which of the following is a benefit of using a database abstraction layer like SQLAlchemy Core?

   • AIt eliminates the need for SQL knowledge
   • BIt allows the same code to work with multiple database backends
   • CIt automatically creates database backups
   • DIt guarantees faster query execution than raw SQL
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