PostgreSQL Objective Questions & Answers for Practitioners Set-1
1. What is the purpose of the JOIN clause in a PostgreSQL SELECT statement?
Explanation: The JOIN clause is used to combine data from multiple tables based on related columns. It allows you to retrieve information from multiple tables in a single query by specifying the relationship between the tables
2. What does the term "MVCC" stand for in the context of PostgreSQL?
Explanation: MVCC (Multi-Version Concurrency Control) is a technique used by PostgreSQL to manage concurrent access to data, allowing multiple transactions to work independently without blocking each other.
3. Which PostgreSQL data type is used to store large binary objects, such as images or documents?
Explanation: The BYTEA data type in PostgreSQL is used to store large binary objects, such as images or documents, in a binary format.
4. In PostgreSQL, what is the purpose of the pg_hba.conf file?
Explanation: The pg_hba.conf file in PostgreSQL is used to configure the client authentication rules and connection parameters, determining how clients can connect to the PostgreSQL server.
5. Which statement is used to add a new column to an existing PostgreSQL table?
Explanation: The ALTER TABLE ADD COLUMN statement is used in PostgreSQL to add a new column to an existing table.
6. What is the purpose of the pg_stat_statements extension in PostgreSQL?
Explanation: The pg_stat_statements extension in PostgreSQL is used to collect and track statistics about the execution of SQL statements, helping to optimize query performance.
7. Which indexing method in PostgreSQL is suitable for text-based searches with wildcard patterns?
Explanation: The GIN index is suitable for text-based searches with wildcard patterns, making it an excellent choice for full-text search scenarios in PostgreSQL.
8. What is the purpose of the VACUUM command in PostgreSQL?
Explanation: The VACUUM command in PostgreSQL is used to reclaim storage space occupied by dead rows (rows that are no longer needed) and maintain the integrity of the database.
9. Which PostgreSQL authentication method uses an external authentication server?
Explanation: The GSSAPI authentication method in PostgreSQL allows external authentication using a GSSAPI (Generic Security Services Application Programming Interface) server.
10. What is the purpose of the pg_dump utility in PostgreSQL?
Explanation: The pg_dump utility in PostgreSQL is used to create logical backups of a PostgreSQL database, including its data and schema.
11. Which PostgreSQL extension is used for handling JSON data?
Explanation: The jsonb data type and functions provided by the PostgreSQL jsonb extension are used for handling JSON data in a more efficient and flexible manner.
12. What is the primary advantage of using a prepared statement in PostgreSQL?
Explanation: A prepared statement in PostgreSQL is precompiled and parameterized, which prevents SQL injection attacks and can improve execution efficiency, especially when the same query is executed multiple times with different parameter values.
13. What is the purpose of the EXPLAIN command in PostgreSQL?
Explanation: The EXPLAIN command in PostgreSQL is used to display the query execution plan, helping to analyze the performance of a query and optimize it if needed.
14. Which PostgreSQL system catalog contains information about all tables, views, and indexes in the database?
Explanation: The information_schema system catalog in PostgreSQL contains metadata information about all tables, views, and indexes in the database, providing a standard way to access this information.
15. What is the purpose of the pg_ctl utility in PostgreSQL?
Explanation: The pg_ctl utility in PostgreSQL is used to manage background processes and control the PostgreSQL server, including starting, stopping, and restarting the server.
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