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PostgreSQL Tests

    • 15 tests |
    • 210 questions

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Sample PostgreSQL Assessments question Test your knowledge!

In PostgreSQL, which command can you use to create a savepoint within a transaction?

  • BEGIN SAVEPOINT
  • CREATE SAVEPOINT
  • NEW SAVEPOINT
  • INITIALIZE SAVEPOINT

Which of the following statements is true about the MVCC (Multiversion Concurrency Control) feature in PostgreSQL?

  • MVCC allows multiple writers to modify the same data without interference.
  • MVCC prevents the 'phantom read' phenomenon by creating a snapshot of the database at the start of a transaction.
  • MVCC in PostgreSQL means that when a row is being updated, a new version of the row is created and the old version remains visible to other transactions until it's no longer needed.
  • MVCC eliminates the need for read locks altogether and removes the possibility of write conflicts.
  • MVCC is a locking mechanism that requires transactions to obtain locks on all data before it can be processed.

Assuming you have a table named 'employees' with a column 'salary', what would be the result of executing the following PostgreSQL command: 'SELECT COUNT(*) FROM employees WHERE salary = (SELECT MAX(salary) FROM employees);'?

  • It returns the highest salary in the employees table.
  • It returns the number of employees who have the highest salary.
  • It triggers an error because subqueries cannot be used with the COUNT function.
  • It returns the total number of employee records in the table.

Considering the default behavior of PostgreSQL, which of the following statements about transaction isolation levels is TRUE?

  • The 'READ UNCOMMITTED' isolation level is the default and allows for dirty reads.
  • The 'REPEATABLE READ' isolation level is the default and prevents non-repeatable reads, but allows phantom reads.
  • The 'READ COMMITTED' isolation level is the default and balances performance with consistency.
  • The 'SERIALIZABLE' isolation level is the only isolation level that completely prevents all concurrency issues.
  • The 'READ COMMITTED' isolation level prevents dirty, non-repeatable, and phantom reads by default.

Assuming that the table 'products' includes columns named 'id', 'name', and 'price', select the query that employs a CTE (Common Table Expression) in PostgreSQL to calculate the average price of all products.

  • WITH AveragePrice AS (SELECT AVG(price) FROM products) SELECT * FROM Averageprice;
  • SELECT * FROM (SELECT AVG(price) as AveragePrice FROM products) AS subquery;
  • SELECT AVG(price) AS AveragePrice FROM products;
  • WITH AveragePrice AS (SELECT price FROM products) SELECT AVG(price) FROM AveragePrice;
  • WITH RECURSIVE AveragePrice AS (SELECT AVG(price) FROM products) SELECT * FROM AveragePrice;

In the table provided, identify the PostgreSQL command that would create a partial index on the 'orders' table for orders with a total_amount greater than 1000.

  • CREATE INDEX idx_orders_high_amount ON orders (total_amount) WHERE total_amount > 1000;
  • CREATE INDEX idx_orders_high_amount ON orders WHERE total_amount > 1000;
  • CREATE PARTIAL INDEX idx_orders_high_amount ON orders (total_amount > 1000);
  • CREATE INDEX idx_orders_high_amount ON orders (total_amount) CONDITION total_amount > 1000;
  • CREATE INDEX idx_orders_high_amount IF NOT EXISTS ON orders (total_amount > 1000);

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PostgreSQL Assessments Tips

1Understand the Basics

Firm up your foundational knowledge of SQL and PostgreSQL’s unique features. Knowing these are the building blocks for more complex tasks.

2Practice Regularly

Consistency is key. Regular practice familiarizes you with the kind of questions you’ll encounter and helps develop swift, accurate problem-solving skills.

3Time Management

Learn to allocate your time effectively on each question so you can demonstrate the breadth of your knowledge across the entire test.

4Hands-On Experience

Work with PostgreSQL in a practical setting to deepen your understanding and readiness for applied test questions.

5Free Practice Tests

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PostgreSQL Assessments FAQs

What is covered in these tests?

These tests cover PostgreSQL fundamentals like database creation, querying, and administration tasks. You’ll also delve into complex SQL commands, data types, and performance optimization challenges.

How do I prepare for PostgreSQL tests?

Start preparing by strengthening your SQL basics, then focus specifically on PostgreSQL’s distinctive features. Use online resources and tutorials for guided learning, and practice with real-world scenarios as much as possible.

Will these tests help me find a job?

Absolutely. These tests are a valuable tool for showing potential employers your hands-on experience and practical knowledge in PostgreSQL, a crucial aspect for many modern data jobs.

How do employers use these tests?

Employers use these tests as a benchmark to measure a candidate’s technical ability with PostgreSQL, ensuring the individual can effectively manage and utilize databases within their company’s environment.

Where can I practice free PostgreSQL test questions?

The best way to prepare is through practice, and Practice Aptitude Tests offers a variety of free PostgreSQL practice tests. These are designed to mirror the questions you’ll face in real assessment scenarios.