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.
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Practice Test
61. In PostgreSQL, which statement is used to insert data into a table?
A. INSERT
B. UPDATE
C. DELETE
D. SELECT
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Answer: INSERT
62. What is the purpose of the "UPDATE" statement in PostgreSQL?
A. To modify existing records in a table
B. To delete records from a table
C. To create a new table
D. To retrieve data from multiple tables
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Answer: To modify existing records in a table
63. What does the "DELETE" statement in PostgreSQL do?
A. Removes records from a table
B. Modifies records in a table
C. Adds new records to a table
D. Combines data from multiple tables
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Answer: Removes records from a table
64. In PostgreSQL, which clause is used to filter the result set of a SELECT statement?
A. WHERE
B. JOIN
C. ORDER BY
D. GROUP BY
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Answer: WHERE
65. What is the purpose of the "COMMIT" statement in PostgreSQL transactions?
A. To permanently save changes to the database
B. To undo changes made during a transaction
C. To start a new transaction
D. To lock the database for exclusive access
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Answer: To permanently save changes to the database
66. What is a PostgreSQL transaction?
A. A sequence of one or more SQL statements treated as a single unit of work
B. A table that stores transaction history
C. A single SQL statement
D. A group of connected databases
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Answer: A sequence of one or more SQL statements treated as a single unit of work
67. What is the role of the "ROLLBACK" statement in PostgreSQL transactions?
A. To undo changes made during a transaction and restore the original state
B. To save changes to the database
C. To start a new transaction
D. To lock the database for exclusive access
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Answer: To undo changes made during a transaction and restore the original state
68. In PostgreSQL, what does the "SAVEPOINT" statement do within a transaction?
A. Sets a point within a transaction to which you can later roll back
B. Commits the transaction to save changes
C. Aborts the transaction and starts a new one
D. Locks the database for exclusive access
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Answer: Sets a point within a transaction to which you can later roll back
69. What does the "BEGIN" statement do in PostgreSQL transactions?
A. Initiates a new transaction
B. Commits the transaction to save changes
C. Rolls back the transaction
D. Locks the database for exclusive access
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Answer: Initiates a new transaction
70. In PostgreSQL, what is a "nested transaction"?
A. A transaction within another transaction
B. A read-only transaction
C. A transaction with multiple savepoints
D. A transaction involving multiple databases
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Answer: A transaction within another transaction
