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Questions and Answers
What is the primary goal of data normalization?
Which normal form ensures that non-prime attributes depend on the entire primary key?
What is a functional dependency between two attributes X and Y?
Which normalization technique involves moving a group of attributes that are not fully functional dependent on the primary key to a separate table?
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What is the purpose of Boyce-Codd Normal Form (BCNF)?
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What is the result of eliminating data redundancy and inconsistencies?
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What is a characteristic of a table in First Normal Form (1NF)?
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What is a transitive dependency?
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What is the primary benefit of transaction isolation in database systems?
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Which isolation level allows a transaction to read uncommitted changes made by other transactions?
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What is a phantom read in transaction isolation?
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What is the purpose of locking mechanisms in transaction isolation?
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What is the main difference between optimistic and pessimistic concurrency control?
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What is the highest level of isolation in database systems?
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What is a non-repeatable read in transaction isolation?
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What is the purpose of shared locks in transaction isolation?
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Study Notes
Data Normalization
Data normalization is the process of organizing data in a database to minimize data redundancy and dependency.
Reasons for Normalization
- Eliminate data redundancy and inconsistencies
- Improve data integrity
- Reduce data storage requirements
- Improve scalability and flexibility
- Simplify database design and maintenance
Normal Forms
-
First Normal Form (1NF)
- Each table cell must contain a single value
- No repeating groups or arrays
-
Second Normal Form (2NF)
- 1NF is satisfied
- Non-prime attributes must depend on the entire primary key
-
Third Normal Form (3NF)
- 2NF is satisfied
- If a table is in 2NF and a non-prime attribute depends on another non-prime attribute, then it should be moved to a separate table
-
Boyce-Codd Normal Form (BCNF)
- 3NF is satisfied
- A table is in BCNF if and only if it is in 3NF and there are no transitive dependencies
-
Higher Normal Forms
- 4NF, 5NF, and higher normal forms exist, but are less commonly used
Functional Dependencies
- A functional dependency exists between two attributes X and Y if the value of Y is determined by the value of X
- Notation: X → Y (X determines Y)
- Types of dependencies:
- Full functional dependency: X → Y and X is a superkey
- Partial dependency: X → Y, but X is not a superkey
- Transitive dependency: X → Y and Y → Z, then X → Z
Normalization Techniques
- Eliminate Repeating Groups: move repeating groups to a separate table
- Move to Separate Table: move a group of attributes that are not fully functional dependent on the primary key to a separate table
- Split Tables: split a table into two or more tables to eliminate redundancy
Data Normalization
- Data normalization is the process of organizing data in a database to minimize data redundancy and dependency
Reasons for Normalization
- Eliminate data redundancy and inconsistencies
- Improve data integrity
- Reduce data storage requirements
- Improve scalability and flexibility
- Simplify database design and maintenance
Normal Forms
First Normal Form (1NF)
- Each table cell must contain a single value
- No repeating groups or arrays
Second Normal Form (2NF)
- 1NF is satisfied
- Non-prime attributes must depend on the entire primary key
Third Normal Form (3NF)
- 2NF is satisfied
- If a table is in 2NF and a non-prime attribute depends on another non-prime attribute, then it should be moved to a separate table
Boyce-Codd Normal Form (BCNF)
- 3NF is satisfied
- A table is in BCNF if and only if it is in 3NF and there are no transitive dependencies
Higher Normal Forms
- 4NF, 5NF, and higher normal forms exist, but are less commonly used
Functional Dependencies
- A functional dependency exists between two attributes X and Y if the value of Y is determined by the value of X
- Notation: X → Y (X determines Y)
- Types of dependencies:
- Full functional dependency: X → Y and X is a superkey
- Partial dependency: X → Y, but X is not a superkey
- Transitive dependency: X → Y and Y → Z, then X → Z
Normalization Techniques
- Eliminate Repeating Groups: move repeating groups to a separate table
- Move to Separate Table: move a group of attributes that are not fully functional dependent on the primary key to a separate table
- Split Tables: split a table into two or more tables to eliminate redundancy
Transaction Isolation
- Transaction isolation ensures multiple transactions can execute concurrently without interfering with each other, providing a consistent view of the database as if each transaction were the only one executing.
Isolation Levels
- There are four isolation levels, in order of increasing isolation:
- Read Uncommitted: allows reading uncommitted changes made by other transactions
- Read Committed: guarantees seeing only committed changes made by other transactions
- Repeatable Read: ensures a consistent view of the database, but may see phantom rows
- Serializable: ensures a consistent view of the database, as if the transaction were the only one executing
Isolation Anomalies
- Dirty Read: reading uncommitted changes made by another transaction
- Non-Repeatable Read: reading a row modified by another transaction
- Phantom Read: reading a row inserted by another transaction
Locking Mechanisms
- Shared Locks: allow multiple transactions to read a resource, but prevent writing
- Exclusive Locks: allow a transaction to write to a resource, preventing other transactions from accessing it
Concurrency Control
Optimistic Concurrency Control
- Detects conflicts between transactions without using locks
- Transactions validate their changes before committing to ensure consistency
Pessimistic Concurrency Control
- Prevents conflicts between transactions using locks
- Transactions acquire locks on resources to ensure exclusive access
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Description
This quiz covers the process of data normalization in databases, including reasons for normalization and the different normal forms such as 1NF.
