Database Interaction GPYC Practice Questions (Page 3)

Questions 11–15

1. 11application · medium

   A Python script performs a DELETE operation on a MySQL table. The script should log an error and roll back the transaction if the delete fails due to a foreign key constraint. Which exception handling approach is correct?

   • ACatch the error, call commit(), and then retry the delete.
   • BCatch the generic Exception, log the error, and continue without rollback.
   • CIgnore the exception and let the script terminate.
   • DCatch the database-specific IntegrityError, log the error, and call rollback().
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2. 12application · medium

   A company is migrating its Python application from MySQL to PostgreSQL. The application currently uses raw SQL queries with the mysql-connector-python library. The team wants to minimize code changes and make the database layer more portable. Which approach best achieves this?

   • ARewrite all queries to use PostgreSQL-specific syntax and update the connection code.
   • BUse an ORM like SQLAlchemy and define models that abstract the database differences.
   • CKeep using mysql-connector-python but change the connection string to point to PostgreSQL.
   • DUse a custom wrapper that translates MySQL syntax to PostgreSQL syntax at runtime.
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4. 13application · medium

   A Python script connects to a PostgreSQL database and performs a series of INSERT statements. If one INSERT fails due to a constraint violation, the script must log the error and continue with the remaining inserts, but it must not leave the earlier inserts in a partial state. What is the correct error-handling pattern?

   • AUse autocommit mode and catch exceptions per statement.
   • BWrap the entire batch in one try/except and call connection.rollback() only if any insert fails.
   • CCall connection.commit() after each INSERT, and catch exceptions globally.
   • DWrap each INSERT in its own try/except, and call connection.rollback() in the except block before continuing.
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5. 14application · medium

   A developer is using SQLAlchemy Core to query a SQLite database. The query returns thousands of rows, and the developer wants to process them one at a time without loading all rows into memory at once. Which approach should be used?

   • AUse result.fetchall() and iterate over the returned list.
   • BUse result.rowcount to determine the number of rows and then index into the result.
   • CUse result.scalar() to get a single value and repeat the query.
   • DUse result.fetchmany(size) in a loop until no more rows remain.
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6. 15application · medium

   A Python application connects to an Oracle database. The connection may fail due to network issues, and queries may fail due to constraint violations. The developer wants to handle these failures gracefully without crashing the application. Which exception-handling strategy is most appropriate?

   • ALet all exceptions propagate to the top-level and terminate the script.
   • BCatch only the generic Exception class and log the error message.
   • CWrap each database operation in a try/except block that catches the database driver's base exception class.
   • DUse a bare except: clause to catch every possible error.
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