PCPP2 Database Access Practice Test 2 — 15 Questions

Question 1

You are using SQLAlchemy's relationship() function. What does 'back_populates' achieve?

Accepted Answer

It synchronizes the two sides of the relationship in Python memory.. It links two sides of a relationship so that changes in one are reflected in the other via the session's identity map.

Answer

It improves query performance.

Answer

It automatically cascades deletes.

Answer

It forces a database level foreign key constraint.

Question 2

Which Python library is the standard built-in interface for SQLite databases?

Accepted Answer

sqlite3. The 'sqlite3' module is part of the Python standard library.

Answer

pymongo

Answer

sqlalchemy

Answer

db-api

Question 3

Which command-line tool is typically used to inspect the contents of a SQLite database file?

Accepted Answer

sqlite3. The 'sqlite3' command-line interface is the standard tool to interact with .db files.

Answer

mysql

Answer

mongo

Answer

psql

Question 4

What is the purpose of the 'upsert=True' option in MongoDB update operations?

Accepted Answer

It creates a new document if no match is found.. If no document matches the query, a new document is created with the update criteria.

Answer

It prevents duplicates.

Answer

It sorts the results before updating.

Answer

It forces an atomic update across a cluster.

Question 5

When configuring a connection pool in SQLAlchemy, what does the 'pool_size' parameter define?

Accepted Answer

Number of persistent connections kept in the pool.. pool_size defines the number of persistent connections to keep open in the pool.

Answer

The number of retries before failure.

Answer

The timeout duration for queries.

Answer

Maximum number of simultaneous sessions.

Question 6

In SQL, which clause is used to filter results based on a condition after grouping?

Accepted Answer

HAVING. The HAVING clause filters aggregated data, whereas WHERE filters raw data.

Answer

WHERE

Answer

ORDER BY

Answer

GROUP BY

Question 7

In SQLAlchemy, how do you prevent an object from being saved to the database during a session.commit()?

Accepted Answer

session.expunge(obj). You can use session.expunge(obj) to remove the object from the session's management.

Answer

session.delete(obj)

Answer

session.detach(obj)

Answer

session.rollback()

Question 8

How do you retrieve the number of documents matched by a PyMongo 'find' operation without fetching all documents into memory?

Accepted Answer

collection.count_documents(filter). The count_documents() method on a collection is the recommended way to get a count.

Answer

cursor.count()

Answer

collection.size()

Answer

len(list(cursor))

Question 9

Which TWO of the following are valid ways to execute a raw SQL query in SQLAlchemy?

Accepted Answer

Using engine.execute('SELECT * FROM table'). SQLAlchemy allows executing raw SQL via text() with engine.execute() or session.execute().

Answer

Using session.query(RawSQL('SELECT * FROM table'))

Answer

Using session.commit('SELECT * FROM table')

Answer

Using table.run('SELECT * FROM table')

Question 10

You are implementing a custom type in SQLAlchemy. Which method must be overridden to convert data from the database type back to a Python object?

Accepted Answer

process_result_value. The process_result_value method is responsible for type conversion during retrieval.

Answer

load_dialect_impl

Answer

bind_processor

Answer

process_bind_param

Question 11

Which THREE operations are supported by the PyMongo 'bulk_write' method?

Accepted Answer

DeleteOne. bulk_write handles InsertOne, UpdateOne, and DeleteOne operations.

Answer

FindOne

Answer

AggregateOne

Question 12

Which THREE features are provided by SQLAlchemy's Unit of Work pattern?

Accepted Answer

Identity mapping to ensure object uniqueness. The Unit of Work pattern manages changes to objects and ensures they are flushed to the DB in the correct order.

Answer

Direct translation of HTTP requests to SQL

Answer

Automatic creation of tables

Question 13

Which TWO are common pitfalls when working with SQLite databases in a multi-threaded environment?

Accepted Answer

Sharing a single connection object across threads. SQLite connections are not thread-safe by default, and lock contention can occur.

Answer

Memory leaks in the cursor object

Answer

SQL injection via parameterized queries

Answer

Incorrect SQL syntax

Question 14

Which THREE are characteristics of BSON (Binary JSON) as used by MongoDB?

Accepted Answer

It is optimized for efficient traversal. BSON is binary-encoded, supports more types than JSON, and is optimized for traversal.

Answer

It is deprecated in newer MongoDB versions

Answer

It is exactly the same as JSON

Question 15

Which THREE of these are valid relationship loading strategies in SQLAlchemy?

Accepted Answer

subquery. lazy, joined, and subquery are three common loading strategies.

Answer

eager

Answer

direct