PCPP2 Database Access — Timed 10 Questions

Question 1

In a PyMongo application, what happens when you use 'insert_many' with 'ordered=False'?

Accepted Answer

The driver attempts to insert all documents regardless of individual failures.. If 'ordered' is False, the driver continues to insert subsequent documents even if one fails.

Answer

The driver ignores all errors.

Answer

Documents are inserted in parallel.

Answer

The operation stops at the first error.

Question 2

When using SQLAlchemy Declarative Base, how do you define a table name that differs from the class name?

Accepted Answer

Set __tablename__ = 'name'. The __tablename__ attribute is used to explicitly map a class to a specific table name.

Answer

Set __table_name__ = 'name'

Answer

Map it in the metadata object.

Answer

Use the 'table' argument in the class definition.

Question 3

In SQLAlchemy, what is the difference between 'lazy='select'' and 'lazy='joined'' loading strategies?

Accepted Answer

select loading executes a separate SQL statement when the attribute is first accessed.. joined loading performs an outer join to fetch related objects in the same query, whereas select loading fetches them only when accessed.

Answer

joined loading causes N+1 query problems.

Answer

joined loading is always faster.

Answer

select loading is the default for all relationships.

Question 4

You are using SQLAlchemy with an asynchronous driver (asyncio). Which object must be used to perform database operations asynchronously?

Accepted Answer

AsyncSession. AsyncSession is the required class for asynchronous session management in SQLAlchemy.

Answer

Engine.async

Answer

None of the above

Answer

AsyncConnection

Answer

Session

Question 5

You are developing an application using SQLAlchemy and need to retrieve a single object by its primary key. Which method is preferred for this operation?

Accepted Answer

session.get(Model, pk). The get() method on the Session object is the optimized way to retrieve an object by its primary key.

Answer

Model.find(pk)

Answer

session.fetch(Model, pk)

Answer

session.query(Model).filter(Model.id == pk).first()

Question 6

You are using sqlite3 in Python and need to ensure that data integrity is maintained when performing multiple related INSERT operations. Which method should you call on the connection object to commit your changes?

Accepted Answer

connection.commit(). The commit() method is used to save the current transaction to the database.

Answer

connection.save()

Answer

connection.flush()

Answer

cursor.apply()

Question 7

When using the sqlite3 module, what is the primary purpose of using a context manager (the 'with' statement) on a connection object?

Accepted Answer

To automatically commit or rollback transactions.. In sqlite3, the connection context manager automatically commits or rolls back transactions.

Answer

To lock the database file for exclusive access.

Answer

To automatically close the connection upon exit.

Answer

To parse SQL queries for syntax errors.

Question 8

When connecting to a MongoDB instance using PyMongo, what is the role of the 'MongoClient' object?

Accepted Answer

It serves as the main connection handle to the MongoDB cluster.. The MongoClient acts as the entry point to the MongoDB server, allowing access to databases and collections.

Answer

It stores individual documents in memory.

Answer

It defines the schema for BSON documents.

Answer

It translates SQL queries into MQL.

Question 9

Which of the following best describes the benefit of using parameterized queries in sqlite3?

Accepted Answer

They prevent SQL injection attacks.. Parameterized queries prevent SQL injection by separating the query logic from the data.

Answer

They allow for multiple database connections.

Answer

They improve query execution speed by pre-compiling.

Answer

They automatically format the output as JSON.

Question 10

In SQLAlchemy, what does the 'metadata.create_all(engine)' command do?

Accepted Answer

It creates tables for all models bound to the metadata.. It inspects the defined ORM models and emits CREATE TABLE statements to the database.

Answer

It connects to the database and tests the latency.

Answer

It drops all tables and recreates them.

Answer

It populates the tables with initial data.