Normalization in Database
Normalization is a technique of organizing data in a database. The central idea is to eliminate redundant data, which means get rid of duplicates, organize it efficiently, and ensure data dependency makes sense. This concept is part of the SQL domain on Microsoft Azure and holds a significant weight in Microsoft’s “DP-900 Microsoft Azure Data Fundamentals” exam.
The process of normalization involves splitting the database into two or more tables and defining relationships between the tables. The fundamental objective is to isolate data so that adding, modifying, or deleting records doesn’t impact the other tables.
Normalization is done in several stages, referred to as normal forms; each form has a specific level of normalization. The three most used normal forms are the first form (1NF), the second form (2NF), and the third form (3NF).
First Normal Form (1NF):
The primary feature of the first normal form is to eliminate duplicate columns from the same table and create separate tables for each related group of data. For example, consider the following table:
| Student_ID | Name | Subjects |
| 1 | John | English, Math, Science |
| 2 | Sam | English, Art |
Splitting this into 1NF would look like this:
| Student_ID | Name |
| 1 | John |
| 2 | Sam |
The subjects have been removed into a separate table:
| Student_ID | Subject |
| 1 | English |
| 1 | Math |
| 1 | Science |
| 2 | English |
| 2 | Art |
Second Normal Form (2NF):
2NF is a level up from 1NF and introduces a concept called “Functional Dependency”. A functional dependency implies that if the value of one attribute changes, the values of other attributes change as well. All 2NF tables must be in 1NF. For a table to be in 2NF, it must meet the following two conditions: There should be no partial dependencies and no calculated data.
Third Normal Form (3NF):
A table is in 3NF if it is in 2NF and there is no transitive partial dependency. For a table to be in 3NF, every non-key attribute must provide a fact about the key, the whole key, and nothing but the key. In other words, there should not be any dependency between non-prime attributes and partial key dependencies.
Normalization has several advantages. For example, it reduces data redundancy and inconsistencies, improves data integrity and security, and offers better query performance. However, careful planning is essential when normalizing a database system. Overdoing it may result in loss of performance or added complexity where it is unnecessary. It is always a balance between normalizing for operational efficiency and denormalizing for querying and analysis effectiveness.
In the context of Azure, the service SQL Database supports up to 4TB storage and 99.99% service level agreement, making it a perfect candidate for normalized tables where records are frequently accessed or modified. On the contrary, normalization might not be necessary for Azure Storage or Data Lake services where data is less frequently modified, and the goal is more on large-scale, distributed access and analysis.
Practice Test
True or False: Normalization is a process used in relational database design to reduce data redundancy and improve data integrity.
Answer: True
Explanation: Normalization is indeed used in database design to minimize redundancy and maximize data integrity by ensuring that each piece of data is stored in only one place.
What is the primary goal of normalization?
- A) Reducing data redundancy
- B) Increasing data complexity
- C) Maximizing data errors
- D) Minimizing data sharing
Answer: A) Reducing data redundancy
Explanation: The primary purpose of normalization is to reduce data redundancy, which also minimizes data anomalies during data operations.
True or False: Normalization is only used in SQL Server databases.
Answer: False
Explanation: Normalization is a concept that applies to all relational databases, not just SQL Server. Databases such as MySQL, Oracle, or PostgreSQL also use normalization.
Which of the following is NOT a form of normalization in databases?
- A) First Normal Form
- B) Second Normal Form
- C) Third Message Form
- D) Third Normal Form
Answer: C) Third Message Form
Explanation: Third Normal Form is a valid level of database normalization but Third Message Form is not. Stages of normalization include first, second, third, Boyce-Codd, fourth and fifth normal forms.
What is the disadvantage of database normalization?
- A) Reduces data redundancy
- B) Increases data integrity
- C) Can lead to increased query complexity
- D) Streamlines data operations
Answer: C) Can lead to increased query complexity
Explanation: While normalization has many advantages, a potential disadvantage is that it can lead to more complex queries because data may be spread across different tables.
True or False: In the normalization process, data is generally spread across multiple tables.
Answer: True
Explanation: The process of normalization involves organizing data in such a way that it is distributed into various tables- thereby reducing redundancies.
Which level of normalization is mostly applied in practical cases?
- A) First Normal Form
- B) Second Normal Form
- C) Third Normal Form
- D) Fourth Normal Form
Answer: C) Third Normal Form
Explanation: In most real-world cases, normalization up to the third normal form is considered sufficient.
True or False: Normalization promotes data duplication.
Answer: False
Explanation: One of the main reasons for using normalization is to prevent data duplication or redundancy, not to promote it.
Database normalization is carried until the ______ is achieved.
- A) Data duplicity
- B) Data integrity
- C) Data querying
- D) Data complexity
Answer: B) Data integrity
Explanation: Normalization continues until data integrity- the assurance of the accuracy and consistency of data- is achieved.
True or False: Denormalization is the process of consolidating data to improve read performance.
Answer: True
Explanation: Denormalization is indeed the process of increasing redundancy in a database to improve data read performance at the cost of some write performance.
Which of the following is NOT a normal form in the normalization process?
- A) Boyce-Codd Normal Form
- B) Fifth Normal Form
- C) Sixth Normal Form
- D) Query Normal Form
Answer: D) Query Normal Form
Explanation: The stages of normalization include first, second, third, Boyce-Codd, fourth, and fifth normal forms. There is no Query Normal Form.
True or False: Normalization always improves database performance.
Answer: False
Explanation: Although normalization can improve the logical design of a database, it can sometimes lead to performance issues due to increased complexity in queries.
Interview Questions
Question: What exactly is normalization in the context of databases?
Normalization is a database design technique that reduces data redundancy and eliminates undesirable characteristics like Insertion, Update and Deletion Anomalies.
Question: What is the main purpose of normalization?
The primary purpose of normalization is to eliminate data redundancy, which in turn reduces the disk storage space needed for the data set. It also arranges data in such a way that it can be modified, retrieved, and sorted most efficiently.
Question: How many forms of normalization are there, commonly?
There are commonly five forms of normalization: First Normal Form (1NF), Second Normal Form (2NF), Third Normal Form (3NF), Boyce-Codd Normal Form (BCNF), and Fourth Normal Form (4NF).
Question: Describe First Normal Form (1NF) in database normalization.
In the First Normal Form (1NF), each table cell should contain a single value, and each record needs to be unique.
Question: What is the principle of Second Normal Form (2NF) in database normalization?
The Second Normal Form (2NF) states that it should be in First Normal Form and also the column data should be dependent on the whole primary key.
Question: Can you explain the Third Normal Form (3NF) in database normalization?
The Third Normal Form (3NF) states that it should be in Second Normal Form and also none of its columns is transitive with the primary key, which means no non-primary attributes should depend on other non-primary attributes.
Question: What is the Fourth Normal Form (4NF) in database normalization?
The Fourth Normal Form (4NF) states that a database should be free of non-trivial multivalued dependency, which means a record’s attributes should not depend on each other.
Question: How does normalization increase the efficiency of a database?
Normalization increases the efficiency of a database by reducing data redundancy, facilitating data consistency, and making it easier to maintain the database.
Question: What are Insertion, Update and Deletion Anomalies in a database?
Insertion, Update and Deletion Anomalies are potential problems in a database. An insertion anomaly occurs when certain attributes cannot be inserted into the database without the presence of other attributes. An update anomaly occurs when certain attributes are changed, leading to inconsistencies. A deletion anomaly occurs when certain attributes are deleted, causing loss of data.
Question: Can you give a downside to database normalization?
A potential downside of normalization is that it can lead to increased complexity and overhead because data is distributed among more tables. This can potentially lead to decreased performance when querying data.
Question: What is denormalization?
Denormalization is the process of adding redundancy to a normalized database for the purpose of improving read performance.
Question: In what scenarios might denormalization be useful?
Denormalization might be useful in scenarios where read performance needs to be optimized at the expense of write performance, for example in a database that is read-heavy and write-light.
Question: How does normalization help in keeping the database consistent?
Normalization ensures that each piece of data has a single source of truth, thereby keeping the database consistent. Without normalization, the same piece of data might be duplicated in multiple places, leading to potential inconsistencies.
Question: Can we completely eliminate redundancy using normalization?
While normalization reduces redundancy, it does not entirely eliminate it. Some redundancy may still be needed for performance optimization.
Question: What is Third Normal Form (3NF) in terms of functional dependencies?
In terms of functional dependencies, Third Normal Form (3NF) can be defined as a database schema being in 2NF and every non-prime attribute being non-transitively dependent on every candidate key of the database.
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