Can a subblock in PL/pgSQL contain other subblocks within it?

d. Yes, subblocks can be nested to any level.

a. Yes, but only one level of nesting is allowed.

b. No, subblocks cannot be nested.

c. Nesting subblocks is possible but not recommended.

What is an index on expression

a. An index created on a function or expression involving one or more columns.

b. An index that is only applicable to text-based columns.

c. An index created on a standard column without modifications.

d. An index created on the result of a mathematical expression.

What is the primary purpose of an index in a relational database?

b. To speed up the retrieval of rows by providing a quick access path to data

a. To enforce primary key constraints

c. To store additional information about the table

d. To create a clustered structure for the table

In SQL, what is the primary purpose of creating an index on a table column?

a. To enhance the speed of queries that search based on the indexed column

b. To increase data insertion speed

c. To restrict data duplication in the indexed column

d. To automatically sort the data in the table

Which of the following INSERT statements uses a subquery to insert the average price from products table into the price_averages table?

INSERT INTO price_averages (average_price) VALUES (SELECT AVG(price) FROM products);

INSERT INTO price_averages (average_price) SELECT AVG(price) FROM products:

INSERT INTO price_averages VALUES (SELECT AVG(price) FROM products);

INSERT INTO price_averages SELECT AVG(price) VALUES FROM products;

What is the purpose of the WITH CHECK OPTION clause when creating a view?

b. It ensures that only rows meeting the view's criteria can be inserted or updated through the view.

a. It prevents the view from being updated.

c. It adds a check for NULL values in the view.

d. It enforces the CHECK constraint on the view.

In the context of PostgreSQL. what is a primary difference between CHAR and VARCHAR data types when defining the length and handling of the stored strings?

CHAR(n) pads the stored string with spaces to the length of n, while VARCHAR(n) does not.

CHAR(n) will truncate the stored string to n characters, while VARCHAR(n) will not store more than n characters but will not truncate the extra.

CHAR(n) and VARCHAR(n) both pad the stored string with spaces to the length of n.

VARCHAR(n) pads the stored string with spaces to the length of n. while CHAR(n) does not.

A view named 'DepartmentView' is created with the following SQL command: CREATE VIEW DepartmentView AS SELECT Employees.Name , Departments.DepartmentName FROM Employees JOIN Departments ON Employees. Department = Departments.DepartmentName; Can this view be updated to change an employee's department?

d. No, because the view is based on a JOIN of two tables.

a. No, views cannot be updated under any circumstances.

b. Yes, because the view is created using a simple JOIN.

c. Yes, but only if the department exists in the Departments table.

What is the difference between a view and a table in SQL?

d. Views are based on SELECT queries, and tables store data.

a. Tables store data, while views store metadata.

b. Views cannot be queried, only tables can.

c. Views are physical, and tables are virtual.

What is the main advantage of a B-Tree index? set of possible values

It provides efficient access for both range and exact match queries.

It works best with columns having a limited set of possible values

It is the default index type for most databases.

It is optimized for full-text searches.

How does an index on an expression improve query performance?

By providing faster access to rows that satisfy the expression. table.

By eliminating the need for additional indexes on the table

By reducing the storage space required for the index.

By speeding up all operations on the table.

In SQL, what is a trigger primarily used for?

To execute a specified action when certain conditions are met in the database

To speed up data retrieval operations

To lock tables during complex transactions

What happens if two transactions modify the same data at the same time in PostgreSQL?

One transaction will wait for the other to complete.

O Both modifications are applied simultaneousty

Both transactions are rolled back automatically.

Which of the following is a benefit of using functions in SQL?

Code organization and reusability

What does the EXPLAIN command do in SQL?

It shows the execution plan of query without executing it.

It performs the query and returns the result set.

It explains the syntax of the SQL query

It provides a detailed description of the table structure.

Consider the following view created from the Employees table: CREATE VIEW FinanceEmployees AS SELECT Name. Salary FROM Employees WHERE Department = 'Finance': What happens if you try to insert a new employee into this view who is not part of the Finance department?

The insert will be successful, but the employee will not show in the view.

The view will be automatically updated to include all departments.

The insert operation will fail.

The employee will be added to the Finance department automatically.

Which statement is true about SQL views?

Views can be used to simplify complex queries.

Views allow data insertion but not deletion.

Views are physical data structures stored in the database.

Views increase the storage space in a database.

What is the difference between a stored procedure and a trigger in SQL?

Triggers are automatically executed in response to an event, while stored procedures are manually invoked.

Stored procedures can only be executed during a transaction. while triggers can be executed independently.

Triggers can be called explicitly, while stored procedures cannot.

Stored procedures can only be associated with tables, while triggers can be associated with any database object.

Which of the following statements are true of a view?

A view simplifies how users work with data

A view joins static tables using user-defined parameters.

A view can not insert data into tables

Under the 'Repeatable Read' isolation level, if a transaction T1 reads a set of rows and then another transaction T2 inserts (not commited yet) a new row in that set before T1 completes, what will T1 observe if it re-reads the set?

T1 will not see the new row inserted by T2.

T1 will encounter a serialization error.

T1 will see the new row inserted by T2.

T1's second read will be blocked until T2 commits.

Given a view created with the following SQL statement: CREATE VIEW HRView AS SELECT EmployeeID, Name FROM Employees WHERE Department = 'HR' WITH LOCAL CHECK OPTION; What will happen if you try to update an employee's department to 'IT' through this view?

2)The update operation will fail

1)The update will be successful and the employee will be listed in the 'IT' department.

3)The update will succeed but the employee will remain in the 'HR' department.

4)The LOCAL CHECK OPTION does not affect update operations.

What is a transaction in the context of a relational database?

An isolated, atomic unit of work

A 'statement-level' trigger in PostgreSQL runs:

Only once, regardless of the number of rows affected by the triggering event.

Multiple times in random order during the execution of the triggering event.

Continuously until manually stopped.

Once for each row affected by the triggering event.

What is a superuser in PostgreSQL?

A user that has access to all commands and features.

A user that can log in to the PostgreSQL database.

A role that is automatically created when the database is installed.

A role that can create other roles.

In PostgreSQL, what is the significance of a role with the REPLICATION attribute?

It grants the role the ability to initiate streaming replication.

It is used for roles that manage database connections.

It designates the role as part of the database replication schema.

It allows the role to perform database bel up operations.

What distinguishes a stored procedure in SQL from a simple SQL query?

Stored procedures can execute multiple SQL statements in a single call, allowing for complex operations.

Stored procedures are primarily used for data visualization, unlike SQL queries.

Stored procedures can only retrieve data, while SQL queries can modify data.

Stored procedures are written in a different programming language than SQL.

Can a trigger in PostgreSQL call a function written in a language other than SQL or PL/pgSQL?

Yes, any language supported by PostgreSQL can be used.

No, only SQL can be used in triggers.

No, only PL/pgSQL can be used in triggers.

Yes, but only if the language has explicit support for triggers.

What is a row-level trigger in PostgreSQL?

A trigger that is executed for each row affected by the triggering event.

A trigger that aggregates data across multiple rows.

A trigger that operates on the entire table at once.

A trigger that activates only when a specific row is queried.

How does PostgreSQL treat variables defined in a subblock in relation to variables in the outer block?

Variables in the outer block are not accessible from the subblock.

Variables in the subblock are automatically global.

Variables in the subblock cannot have the same name as in the outer block.

Variables in the subblock override variables with the same name in the outer block.

In the context of SQL databases, what does the ACID property of transactions ensure?

Atomicity, Consistency, Isolation, Durability

Automated Commit and Immediate Deletion

Advanced Control of Indexed Data

Atomicity, Confidentiality, Integrity, and Durability

In SQL, what is a key characteristic of a materialized view compared to a standard view?

Materialized views store the result set of the query

Materialized views cannot include JOIN operations

Materialized views can only display data from one table

Materialized views update their data in real-time

What is the primary drawback of adding too many indexes to a table?

Adds overhead to data manipulation operations like insert, update, and delete.

Increases the time required for read operations.

Reduces the efficiency of the B-Tree algorithm.

Limits the types of queries that can be executed.

What is a major advantage of using views in SQL?

Enhanced security by restricting access to certain columns

How does the SQL SAVEPOINT statement differ from the ROLLBACK statement?

SAVEPOINT is used to mark a point in a transaction. while ROLLBACK is used to undo changes.

SAVEPOINT and ROLLBACK serve the same purpose in a transaction.

SAVEPOINT , used to end a transaction, while ROLLBACK is used to undo changes.

SAVEPOINT is used to commit changes, while ROLLBACK is used to initiate a nested transaction.

What is the role of the 'SAVEPOINT' command in SQL transactions?

It marks specific point within a transaction to which you can later roll back.

It initiates a new transaction within the current transaction.

it permanently saves all changes made in the transaction up to that point.

it synchronizes transactions running on different databases.

What is a trigger in PostgreSQL?

A special kind of stored procedure that runs automatically when certain events occur in a database table.

A tool for managing user permissions on a database.

A function for calculating aggregated data.

What are subblocks in the context of PostgreSQL stored procedures?

Blocks nested within another block.

Separate procedures called within a main procedure.

Syntax errors within a procedure.

Data blocks in the database related to procedures.

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c. It creates necessary indexes for the query.

d. It modifies the query to run faster.

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