20 Lecture - Second Normal Form

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20 Lecture

CS403

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Second Normal Form

Second Normal Form (2NF) is a normalization concept in database design. It requires that each non-key attribute in a table is dependent on the entire primary key and not just a part of it. It eliminates partial dependencies and ensures that each


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  1. What is Second Normal Form (2NF)? a. It is a database modeling technique to eliminate data redundancy b. It is a normalization concept that ensures all non-key attributes are dependent on the entire primary key c. It is a type of database join d. It is a database indexing technique Answer: b. It is a normalization concept that ensures all non-key attributes are dependent on the entire primary key. Which of the following is a violation of Second Normal Form? a. A table has a composite primary key b. A table has a non-key attribute that depends on only part of the primary key c. A table has repeating groups of data d. A table has a single primary key attribute Answer: b. A table has a non-key attribute that depends on only part of the primary key. What is the first step in achieving Second Normal Form? a. Eliminating data redundancy b. Defining a primary key for the table c. Removing null values from the table d. Applying functional dependencies to the table Answer: b. Defining a primary key for the table. Which normal form is 2NF based on? a. First Normal Form (1NF) b. Third Normal Form (3NF) c. Fourth Normal Form (4NF) d. Fifth Normal Form (5NF) Answer: a. First Normal Form (1NF). Which of the following is a benefit of Second Normal Form? a. Improved query performance b. Reduced data storage space c. Improved data integrity d. Increased data redundancy Answer: c. Improved data integrity. Which type of dependency does Second Normal Form eliminate? a. Full dependency b. Partial dependency c. Transitive dependency d. Multivalued dependency Answer: b. Partial dependency. Which of the following is an example of a violation of Second Normal Form? a. A table with a single primary key attribute b. A table with a composite primary key c. A table with a non-key attribute that depends on another non-key attribute d. A table with a non-key attribute that depends on the entire primary key Answer: c. A table with a non-key attribute that depends on another non-key attribute. What is the purpose of normalizing a database to Second Normal Form? a. To eliminate null values from the table b. To eliminate data redundancy c. To improve query performance d. To increase data redundancy Answer: b. To eliminate data redundancy. Which of the following is a characteristic of a table in Second Normal Form? a. Each non-key attribute is dependent on the entire primary key b. Each non-key attribute is dependent on a part of the primary key c. The table has repeating groups of data d. The table has no primary key Answer: a. Each non-key attribute is dependent on the entire primary key. What is the difference between First Normal Form (1NF) and Second Normal Form (2NF)? a. 1NF eliminates partial dependencies, while 2NF eliminates repeating groups b. 1NF eliminates repeating groups, while 2NF eliminates partial dependencies c. 1NF eliminates transitive dependencies, while 2NF eliminates partial dependencies d. 1NF eliminates null values, while 2NF eliminates partial dependencies Answer: b. 1NF eliminates repeating groups, while 2NF eliminates partial dependencies.


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  1. What is Second Normal Form (2NF)? Answer: Second Normal Form (2NF) is a database normalization concept that ensures that all non-key attributes are dependent on the entire primary key, and not just a part of it. What is the purpose of achieving Second Normal Form? Answer: The purpose of achieving Second Normal Form is to eliminate partial dependencies and ensure data integrity. How do you identify partial dependencies in a table? Answer: Partial dependencies can be identified by looking for non-key attributes that depend on only a part of the primary key. Can a table in Second Normal Form have composite primary keys? Answer: Yes, a table in Second Normal Form can have composite primary keys. What is the difference between First Normal Form (1NF) and Second Normal Form (2NF)? Answer: First Normal Form eliminates repeating groups of data, while Second Normal Form eliminates partial dependencies. How can you achieve Second Normal Form? Answer: To achieve Second Normal Form, the table must be in First Normal Form and then all partial dependencies must be removed. What is an example of a table that violates Second Normal Form? Answer: A table that has a non-key attribute that depends on only a part of the primary key violates Second Normal Form. What are some benefits of having a database in Second Normal Form? Answer: Some benefits of having a database in Second Normal Form include improved data integrity, reduced data redundancy, and easier data maintenance. Can a table be in Second Normal Form without being in First Normal Form? Answer: No, a table must be in First Normal Form before it can be in Second Normal Form. Can a table in Second Normal Form have non-key attributes that are not dependent on the primary key? Answer: No, all non-key attributes in a table in Second Normal Form must be dependent on the entire primary key.

Second Normal Form (2NF) is a database normalization concept that builds upon First Normal Form (1NF) by ensuring that all non-key attributes are dependent on the entire primary key, and not just a part of it. This eliminates partial dependencies and ensures data integrity. To achieve Second Normal Form, the table must first be in First Normal Form, meaning that there are no repeating groups of data. Then, all partial dependencies must be removed. Partial dependencies occur when a non-key attribute is dependent on only a part of the primary key. For example, consider a table of customer orders, with the primary key being (customer_id, order_id). If the table has an attribute for product_name that is dependent on the order_id alone, it violates Second Normal Form. To correct this, the table should be split into two separate tables, one for customer information and one for order information, with the product_name attribute in the order table. By achieving Second Normal Form, a database can have improved data integrity, reduced data redundancy, and easier data maintenance. It can also facilitate more efficient querying and manipulation of data. However, it is important to note that achieving higher normal forms, such as Third Normal Form and beyond, can result in more complex database designs and potentially slower performance. Therefore, the decision to normalize a database beyond Second Normal Form should be based on the specific needs and goals of the application.

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