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Week 8 Flashcards

1
Q

What does DCL stand for?

A

DCL stands for Data Control Language.

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2
Q

What are the two main commands of DCL?

A

The two main commands of DCL are GRANT and REVOKE.

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3
Q

What is the purpose of the GRANT command in DCL?

A

The purpose of the GRANT command in DCL is to give users specific privileges or permissions on database objects such as tables, views, or procedures.

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4
Q

What is the purpose of the REVOKE command in DCL?

A

The purpose of the REVOKE command in DCL is to take back or remove previously granted permissions or privileges from users.

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4
Q

How does DCL help in database security?

A

DCL helps in database security by controlling user access to database objects and enforcing restrictions, thus preventing unauthorized operations.

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5
Q

What does TCL stand for?

A

TCL stands for Transaction Control Language

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6
Q

What are the main commands of TCL?

A

The main commands of TCL are COMMIT, ROLLBACK, SAVEPOINT, and SET TRANSACTION.

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7
Q

What is the purpose of the COMMIT command in TCL?

A

The purpose of the COMMIT command in TCL is to permanently save the changes made during a transaction to the database.

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7
Q

What is the purpose of the ROLLBACK command in TCL?

A

The purpose of the ROLLBACK command in TCL is to undo changes made during a transaction before they are committed.

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7
Q

What is the difference between SAVEPOINT and ROLLBACK?

A

The difference between SAVEPOINT and ROLLBACK is that SAVEPOINT sets a point in a transaction to which you can later rollback, whereas ROLLBACK undoes all changes made since the beginning of the transaction or since a specified savepoint.

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8
Q

What is a transaction in a database system?

A

A transaction in a database system is a unit of work that is performed against the database, which can include multiple operations like insertions, updates, and deletions, and must be executed in full or not at all.

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8
Q

What are the four properties of a transaction?

A

The four properties of a transaction are ACID: Atomicity, Consistency, Isolation, and Durability.

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9
Q

Why are transactions important for database integrity?

A

Transactions are important for database integrity because they ensure that the database remains in a consistent state, even in cases of failures, by allowing only complete operations to be committed.

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9
Q

How does a transaction help ensure data consistency?

A

A transaction helps ensure data consistency by ensuring that all operations within the transaction are successfully executed before changes are committed, or none at all.

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10
Q

What happens if a transaction fails?

A

If a transaction fails, the database can revert to its previous state using ROLLBACK, undoing all operations within the transaction.

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11
Q

What does ACID stand for in the context of transactions?

A

ACID stands for Atomicity, Consistency, Isolation, and Durability.

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11
Q

What is the ‘Atomicity’ property in ACID?

A

The Atomicity property ensures that all operations within a transaction are completed successfully or none are applied at all.

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11
Q

What is the ‘Consistency’ property in ACID?

A

The Consistency property ensures that a transaction brings the database from one valid state to another, maintaining database integrity.

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12
Q

What is the ‘Isolation’ property in ACID?

A

The Isolation property ensures that transactions are executed independently without interference from other concurrent transactions.

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12
Q

What is the ‘Durability’ property in ACID?

A

The Durability property ensures that once a transaction is committed, its changes are permanently stored in the database, even in the case of a system failure.

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12
Q

What does the COMMIT command do in a transaction?

A

The COMMIT command in a transaction saves all changes made during the transaction to the database permanently.

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13
Q

What does the ROLLBACK command do in a transaction?

A

The ROLLBACK command in a transaction undoes all changes made since the beginning of the transaction or since a savepoint.

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13
Q

What are transaction isolation levels?

A

Transaction isolation levels define the degree to which transactions are isolated from each other in terms of visibility of data changes.

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14
Q

What is the ‘Read Uncommitted’ isolation level?

A

The Read Uncommitted isolation level allows a transaction to read uncommitted changes made by other transactions, potentially leading to dirty reads.

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15
Q

What is the ‘Read Committed’ isolation level?

A

The Read Committed isolation level ensures that a transaction can only read committed data changes made by other transactions, avoiding dirty reads.

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16
Q

What is the ‘Repeatable Read’ isolation level?

A

The Repeatable Read isolation level ensures that if a transaction reads the same data multiple times, the data remains consistent throughout the transaction, preventing non-repeatable reads.

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17
Q

What is the ‘Serializable’ isolation level?

A

The Serializable isolation level ensures complete isolation from other transactions, preventing dirty reads, non-repeatable reads, and phantom reads.

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18
Q

Which isolation level offers the highest level of data integrity?

A

The Serializable isolation level offers the highest level of data integrity.

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18
Q

What is an aggregate function in SQL?

A

An aggregate function in SQL performs a calculation on a set of values and returns a single value, such as SUM or AVG.

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19
Q

What does the COUNT function do?

A

The COUNT function returns the number of rows in a set.

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20
Q

What does the SUM function do?

A

The SUM function returns the total sum of a numeric column.

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20
Q

What does the AVG function do?

A

The AVG function returns the average value of a numeric column.

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21
Q

What does the MAX function do?

A

The MAX function returns the maximum value from a set of values.

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22
Q

What does the MIN function do?

A

The MIN function returns the minimum value from a set of values.

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23
Q

What is a scalar function in SQL?

A

A scalar function in SQL returns a single value based on the input values, such as UPPER or LOWER.

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24
Q

What does the UPPER function do?

A

The UPPER function converts a string to uppercase.

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25
Q

What does the LOWER function do?

A

The LOWER function converts a string to lowercase.

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26
Q

What does the LEN function do?

A

The LEN function returns the length of a string.

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27
Q

What does the ROUND function do?

A

The ROUND function rounds a numeric value to a specified number of decimal places.

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27
Q

What does the GETDATE function return?

A

The GETDATE function returns the current date and time.

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28
Q

What is a sequence in SQL?

A

A sequence in SQL is an object that generates a sequence of numeric values.

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28
Q

How is a sequence created in SQL?

A

A sequence is created using the CREATE SEQUENCE statement in SQL.

29
Q

What is the purpose of a sequence in database management?

A

The purpose of a sequence in database management is to automatically generate unique values, often for primary keys.

30
Q

How can you retrieve the next value of a sequence in SQL?

A

You can retrieve the next value of a sequence in SQL using the NEXTVAL keyword.

31
Q

What is the difference between a sequence and an auto-increment?

A

The difference between a sequence and an auto-increment is that a sequence is more flexible and can be used across multiple tables, while auto-increment is tied to a single column in a table.

31
Q

What is a trigger in a database?

A

A trigger in a database is a stored procedure that is automatically executed in response to certain events on a table, such as insertions or updates.

32
Q

What is a BEFORE trigger?

A

A BEFORE trigger is fired before an event occurs on a table.

33
Q

What is an AFTER trigger?

A

An AFTER trigger is fired after an event occurs on a table.

34
Q

What is an INSTEAD OF trigger?

A

An INSTEAD OF trigger is fired in place of an event, allowing you to override the default behavior.

35
Q

What are common use cases of triggers?

A

Common use cases of triggers include auditing changes, enforcing business rules, and updating related tables.

35
Q

What is a User Defined Function (UDF)?

A

A User Defined Function (UDF) is a function created by a user to perform specific calculations or actions within SQL queries.

36
Q

What are the benefits of using UDFs in SQL?

A

Benefits of using UDFs in SQL include reusability, modularity, and the ability to perform complex calculations within queries.

37
Q

What is the difference between a UDF and a stored procedure?

A

The difference between a UDF and a stored procedure is that a UDF can be used within SQL queries like a scalar function, while a stored procedure cannot.

38
Q

How do you create a UDF in SQL?

A

You create a UDF in SQL using the CREATE FUNCTION statement.

39
Q

What is a stored procedure in a database?

A

A stored procedure in a database is a precompiled set of one or more SQL statements stored under a name and executed as a unit.

40
Q

What are the benefits of using stored procedures?

A

Benefits of using stored procedures include better performance, reusability, and security.

40
Q

How do you pass parameters to a stored procedure?

A

You pass parameters to a stored procedure using input, output, or both types of parameters defined in the procedure.

40
Q

How do you create a stored procedure in SQL?

A

You create a stored procedure in SQL using the CREATE PROCEDURE statement.

41
Q

What is the Optional class in Java used for?

A

The Optional class in Java is used to represent a value that may or may not be present.

42
Q

How do you create an empty Optional in Java?

A

You create an empty Optional in Java using Optional.empty().

43
Q

How do you check if a value is present in an Optional?

A

You check if a value is present in an Optional using the isPresent() method.

44
Q

What is the purpose of Optional.of() in Java?

A

The purpose of Optional.of() in Java is to create an Optional with a non-null value.

45
Q

How can Optional.ifPresent() be used?

A

Optional.ifPresent() can be used to execute a block of code if a value is present.

46
Q

What is the Stream API in Java?

A

The Stream API in Java is used to process collections of objects in a functional style.

47
Q

What are the two types of operations in the Stream API?

A

The two types of operations in the Stream API are intermediate operations (e.g., map, filter) and terminal operations (e.g., forEach, reduce).

48
Q

How do you create a stream from a collection in Java?

A

You create a stream from a collection in Java using the stream() method.

49
Q

What is the difference between map and filter in the Stream API?

A

The difference between map and filter in the Stream API is that map transforms elements, while filter selects elements based on a condition.

50
Q

What does the reduce method do in the Stream API?

A

The reduce method in the Stream API combines elements of a stream into a single result.

51
Q

What is the Reflection API in Java?

A

The Reflection API in Java allows programs to inspect and manipulate classes, methods, and fields at runtime.

52
Q

What is the main use of the Reflection API?

A

The main use of the Reflection API is for dynamic class loading, inspecting or modifying the behavior of methods and fields at runtime.

53
Q

How can you obtain a class object using reflection?

A

You can obtain a class object using reflection with Class.forName(“ClassName”).

53
Q

How can you get methods of a class using the Reflection API?

A

You can get methods of a class using the getMethods() or getDeclaredMethods() method in the Reflection API.

54
Q

What are some risks of using reflection?

A

Risks of using reflection include performance overhead and possible violation of encapsulation.

54
Q

What is the Thread class in Java?

A

The Thread class in Java represents a thread of execution.

55
Q

How do you start a new thread in Java using the Thread class?

A

You start a new thread in Java using the start() method of the Thread class.

55
Q

What method is used to stop a thread in Java?

A

The method used to stop a thread in Java is interrupt(), though thread stopping is generally managed via a flag.

56
Q

What is the difference between run() and start() in threads?

A

The difference between run() and start() is that start() creates a new thread, while run() simply executes code on the current thread.

57
Q

What is the Runnable interface in Java?

A

The Runnable interface in Java represents a task that can be executed by a thread.

57
Q

How is Runnable different from Thread?

A

Runnable is different from Thread in that Runnable is an interface for defining tasks, while Thread is a class that executes tasks.

57
Q

How do you implement the Runnable interface in Java?

A

You implement the Runnable interface in Java by creating a class that implements Runnable and providing the run() method.

58
Q

What are the different states of a thread in Java?

A

The different states of a thread in Java are NEW, RUNNABLE, BLOCKED, WAITING, TIMED_WAITING, and TERMINATED.

59
Q

What is the ‘NEW’ thread state in Java?

A

The NEW thread state is when a thread is created but has not started execution.

60
Q

What is the ‘RUNNABLE’ thread state in Java?

A

The RUNNABLE thread state is when a thread is executing or ready to execute.

61
Q

What is the ‘BLOCKED’ thread state in Java?

A

The BLOCKED thread state is when a thread is waiting to acquire a lock.

62
Q

What is the ‘WAITING’ thread state in Java?

A

The WAITING thread state is when a thread is waiting indefinitely for another thread to perform a particular action.

63
Q

What is the ‘TERMINATED’ thread state in Java?

A

The TERMINATED thread state is when a thread has completed execution.

64
Q

What is multithreading in Java?

A

Multithreading in Java allows multiple threads to execute concurrently, sharing resources.

65
Q

How does multithreading improve performance in Java?

A

Multithreading improves performance by allowing tasks to be executed simultaneously, making better use of CPU resources.

66
Q

What is the main challenge of multithreading?

A

The main challenge of multithreading is managing shared resources and avoiding conflicts like race conditions.

67
Q

What is synchronization in Java?

A

Synchronization in Java ensures that only one thread can access a shared resource at a time.

68
Q

Why is synchronization necessary in multithreaded programs?

A

Synchronization is necessary in multithreaded programs to prevent data corruption and inconsistent states.

69
Q

How do you synchronize a method in Java?

A

You synchronize a method in Java by using the synchronized keyword.

70
Q

What is a synchronized block in Java?

A

A synchronized block in Java allows you to synchronize only part of a method, rather than the whole method.

71
Q

What is a deadlock in Java?

A

A deadlock in Java occurs when two or more threads are blocked forever, each waiting on the other to release a resource.

72
Q

How does a deadlock occur in Java?

A

A deadlock occurs in Java when two threads hold locks on resources and each waits for the other to release its lock.

72
Q

What are the conditions required for a deadlock to occur?

A

The conditions required for a deadlock to occur are mutual exclusion, hold and wait, no preemption, and circular wait.

73
Q

How can you prevent deadlocks in Java?

A

You can prevent deadlocks in Java by avoiding circular wait conditions and using lock hierarchies.

74
Q

What is a livelock in Java?

A

A livelock in Java occurs when two threads keep responding to each other’s actions, but neither can proceed.

75
Q

How is a livelock different from a deadlock?

A

A livelock differs from a deadlock in that in a livelock, threads are actively trying to resolve the situation, but both fail, while in a deadlock, threads are simply stuck.

76
Q

What are the possible solutions for livelocks?

A

Solutions for livelocks include introducing randomness or retries with delays in actions.

77
Q

What is the Producer-Consumer problem in Java?

A

The Producer-Consumer problem in Java is a classic synchronization problem where producers create data and consumers consume it.

78
Q

How do you solve the Producer-Consumer problem using threads?

A

You solve the Producer-Consumer problem using threads by implementing synchronization techniques like wait() and notify().

79
Q

What is the role of synchronization in solving the Producer-Consumer problem?

A

Synchronization ensures that the producer and consumer threads do not access the shared resource (e.g., a buffer) at the same time.

80
Q

What is a bounded buffer in the Producer-Consumer problem?

A

A bounded buffer in the Producer-Consumer problem is a fixed-size data structure where producers place items and consumers retrieve them.

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