Correct Answer:

Explanation

Box 1: READ UNCOMMITTED
Transactions running at the READ UNCOMMITTED level do not issue shared locks to prevent other transactions from modifying data read by the current transaction. READ UNCOMMITTED transactions are also not blocked by exclusive locks that would prevent the current transaction from reading rows that have been modified but not committed by other transactions. When this option is set, it is possible to read uncommitted modifications, which are called dirty reads. Values in the data can be changed and rows can appear or disappear in the data set before the end of the transaction.
Box 2: READ COMMITTED
READ COMMITTED specifies that statements cannot read data that has been modified but not committed by other transactions.
SERIALIZABLE specifies that statements cannot read data that has been modified but not yet committed by other transactions.
Box 3: REPEATABLE READ
REPEATABLE READ specifies that statements cannot read data that has been modified but not yet committed by other transactions and that no other transactions can modify data that has been read by the current transaction until the current transaction completes.
Box 4: SNAPSHOT
If READ_COMMITTED_SNAPSHOT is set to ON, the Database Engine uses row versioning to present each statement with a transactionally consistent snapshot of the data as it existed at the start of the statement.
References:
https://docs.microsoft.com/en-us/sql/t-sql/statements/set-transaction-isolation-level-transact-sql?view=sql-server

Correct Answer:

Explanation

Box 1: Readcommitted
Read Committed: A transaction T1 executing under this isolation level can only access committed data.
Pros: Good compromise between concurrency and consistency.
Cons: Locking and blocking. The data can change when accessed multiple times within the same transaction.
Box 2: Read Uncommitted
Read Uncommitted (aka dirty read): A transaction T1 executing under this isolation level can access data changed by concurrent transaction(s).
Pros: No read locks needed to read data (i.e. no reader/writer blocking). Note, T1 still takes transaction duration locks for any data modified.
Cons: Data is not guaranteed to be transactionally consistent.
Box 3: Serializable
Serializable: A transaction T1 executing under this isolation level provides the highest data consistency including elimination of phantoms but at the cost of reduced concurrency. It prevents phantoms by taking a range lock or table level lock if range lock can't be acquired (i.e. no index on the predicate column) for the duration of the transaction.
Pros: Full data consistency including phantom protection.
Cons: Locking and blocking. The S locks are held for the duration of the transaction that can lower the concurrency.
References:
https://blogs.msdn.microsoft.com/sqlcat/2011/02/20/concurrency-series-basics-of-transaction-isolation-levels/

Correct Answer: B  🗳️

Correct Answer:

Explanation

Bit is a Transact-SQL integer data type that can take a value of 1, 0, or NULL.
Smallint is aT ransact-SQL integer data type that can take a value in the range from -32,768 to 32,767.
int, bigint, smallint, and tinyint (Transact-SQL)
Exact-number data types that use integer data.

References: https://msdn.microsoft.com/en-us/library/ms187745.aspx
https://msdn.microsoft.com/en-us/library/ms177603.aspx

Correct Answer: B  🗳️