190+ PostgreSQL MCQ With Online Practice Test

PostgreSQL, often referred to as Postgres, is a powerful open-source relational database management system (RDBMS) known for its scalability, robustness, and extensibility. It offers advanced features like ACID compliance, support for complex data types, and support for both SQL and NoSQL data. PostgreSQL is highly regarded for its performance, security, and reliability, making it a popular choice for applications ranging from small startups to large enterprises. Its active developer community continuously enhances and maintains the software. PostgreSQL is an excellent choice for data storage, analysis, and management in various domains, including web applications, data warehousing, and geospatial applications.

Practice Test

51. In PostgreSQL, what does a common table expression (CTE) allow you to do?

Answer: Define temporary result sets within a query

52. What is the purpose of the "WINDOW" clause in a PostgreSQL query?

Answer: To define a window frame for window functions

53. Which SQL clause is used to pivot rows into columns in PostgreSQL?

Answer: CASE

54. What is the purpose of the "LATERAL" keyword in a PostgreSQL query?

Answer: To reference columns from the preceding tables in a subquery

55. What is a recursive common table expression (RCTE) in PostgreSQL used for?

Answer: To handle hierarchical data and recursive queries

56. What is the purpose of the "EXISTS" operator in a PostgreSQL query?

Answer: To check if a subquery returns any rows

57. In PostgreSQL, what does the "OVER" clause do in the context of window functions?

Answer: Defines the window frame for the function

58. What is the purpose of the "UNION" operator in PostgreSQL?

Answer: Combines the result sets of two or more SELECT statements, removing duplicates

59. What does the "FULL OUTER JOIN" do in a PostgreSQL query?

Answer: Retrieves all records where there is a match in either the left or right table

60. What does the "WITH ORDINALITY" option do when used with the "UNNEST" function in PostgreSQL?

Answer: Adds an ordinal position to each element in an array
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