What is PostgreSQL?

• A programming language
• A NoSQL database
• An open-source object-relational database
• A web server

What command is used to connect to a PostgreSQL database via terminal?

• pg_connect
• connect_db
• psql
• start_pg

Which command is used to create a new database in PostgreSQL?

• MAKE DATABASE
• CREATE DATABASE
• INIT DATABASE
• NEW DATABASE

Which data type is used for textual data in PostgreSQL?

• CHAR
• VARCHAR
• TEXT
• All of the above

What is the default port for PostgreSQL?

• 1521
• 3306
• 5432
• 8080

What does a LEFT JOIN return?

• Only matching rows
• All rows from left table and matched rows from right
• All rows from both tables
• Only unmatched rows

Which clause groups rows based on common values?

• ORDER BY
• GROUP BY
• PARTITION BY
• FILTER

What is the purpose of the HAVING clause?

• Filters grouped records
• Sorts grouped records
• Joins multiple tables
• Adds a primary key

Which type of JOIN returns only matching rows?

• INNER JOIN
• FULL JOIN
• LEFT JOIN
• OUTER JOIN

What command is used to update data?

• MODIFY
• EDIT
• UPDATE
• CHANGE

What is the purpose of a GIN index?

• Full-text search and array operations
• Numeric calculations
• Speeding up DELETE
• Foreign key constraints

What does the `RETURNING` clause do in INSERT or UPDATE?

• Returns only successful status
• Returns affected rows
• Logs results
• Creates a backup

What are triggers used for?

• Encrypt data
• Run functions on events
• Perform joins
• Modify system settings

What is stored in the WAL (Write-Ahead Log)?

• Debug logs
• Future queries
• Changes before they’re applied
• User passwords

What is the purpose of VACUUM?

• Back up the database
• Remove NULL values
• Reclaim storage and prevent bloat
• Index tables