PostgreSQL is a powerful, open-source relational database management system (RDBMS) that stores and manages data in a structured format. It's known for its reliability, scalability, and advanced features.
Question: What is the purpose of a database schema in PostgreSQL?
Answer: A schema defines the structure of a database, including tables, columns, data types, and relationships. It ensures data consistency and integrity.
Question: Explain the primary key and foreign key concepts in PostgreSQL.
Answer:
- Primary key: A unique identifier for each row in a table.
- Foreign key: References the primary key of another table, creating a relationship.
Question: What is the difference between the VARCHAR and CHAR data types?
Answer: VARCHAR is variable-length, storing only necessary space, while CHAR has a fixed length.
Question: Explain the purpose of the WHERE clause in a SELECT statement.
Answer: Filters results based on conditions.
Question: What are the LIMIT and OFFSET clauses used for?
Answer: Control the number and starting point of rows returned.
Question: How can you perform data modification using UPDATE statements?
Answer: Modifies existing data in a table.
Question: What is the significance of the JOIN operation, and how does it work in PostgreSQL?
Answer: Combines rows from multiple tables based on related columns.
Question: Explain the GROUP BY clause and its role in aggregation operations.
Answer: Groups rows by specified columns and calculates summary statistics.
Question: How can you calculate aggregate functions like COUNT, SUM, and AVG in PostgreSQL?
Answer: Calculate summary statistics for a group of rows.
Question: What is the purpose of an index in PostgreSQL, and how does it optimize query performance?
Answer: Improves query performance by providing faster data retrieval.
Question: Explain the concept of a PostgreSQL view and how it differs from a table.
Answer: A virtual table that presents data from underlying tables.