Database

Question 1

FNF

Answer 1

Each table cell should contain a single value
Each record needs to be unique

Composite key consists of several columns

Question 2

SNF

Answer 2

• BE in FNF
  Single column primary key does not depend on any subset of candidate key relation

Question 3

TNF

Answer 3

• Be in SNF
• No transitive functional dependencies

Question 4

BCNF

Answer 4

If there is more than one Candidate Key

Question 5

Transaction Isolation Levels

Answer 5

-Read Uncommitted

-Read Committed - issue exclusive locks at the time of modification. Prevents Dirty Read. However data can be changed between individual statements

-Repeatable Read - Shared locks are placed on all data read by each statement. Data that has been read cannot be modified

-Snapshot Isolation - Data read at the beginning of the transaction will be the same as the end of the transaction. Snapshot do not block transactions from reading or modifying the data.

-Serializable - the most strict level of isolation. Transactions cannot read nor write any data before the transaction finished

Question 6

Clustered vs non clustered indexes

Answer 6

Clustered indexes are part of the table structure
Non-clustered indexes are a separate structure with pointers to the actual data

Clustered indexes are in most common cases faster