If an attribute can be calculated from other attributes in the class you can

Hello @bmr ,

Thank you for your suggestion, I have implemented the calculated attribute functionality and its almost working as expected. I am facing one issue in a use case, I want this new attribute to be calculated when its null or blank, if the calculated attribute has a value, new value is not needed to be calculated.

I wrote this value check logic using persistable adapter as shown below.

PersistableAdapter obj = new PersistableAdapter(data, null, SessionHelper.getLocale(), new UpdateOperationIdentifier());

obj.load("calculatedAttribute");

String testNumber = (String) obj.get("calculatedAttribute");

if(testNumber==null || StringUtils.isBlank(testNumber)) {

     //method to calculate the attribute value

}

Somehow an exception is being thrown in the obj.load() line, do you have any suggestion as to how we can easily determine if the value is null or not before or after invoking the execute method of business algorithm.

PFA log file with exception stack trace.

When we talk about database management systems, the first thing that comes to mind is how to store and retrieve data efficiently and efficiently. In order to perform these operations, we need entities and attributes. Attributes are the pieces of information that are stored in a database.

There are several different types of attributes, each with its own distinct purpose. In this blog, we will be discussing the concept of attributes and different types of attributes in DBMS with detailed examples. And for a deeper understanding of databases, you can consider taking up MongoDB Certification training which will help you gain more insight into this topic. Till then, let us first start with the definition of an attribute. 

What are the Attributes of DBMS?

In a database management system (DBMS), an attribute is a piece of data that describes an entity. For example, in a customer database, the attributes might be name, address, and phone number. In a product database, the attributes might be name, price, and date of manufacture. Each attribute has a specific data type, such as string, integer, or date. 

Attributes can be used to describe both simple and complex entities. A product, for example, might be described by a single attribute such as name or price. However, it can also be described by multiple attributes such as name, price, and date of manufacture. In addition, some attributes might be used to describe other attributes. For example, an attribute called "color" might describe a product's color.  

Why do we need to Use Attributes?

Attributes are important because they help to describe the entities in a database. They also help to distinguish one entity from another. For example, if two customers have the same name, we can use their address attribute to identify them. Similarly, if two products have the same name, we can use their price or manufacturer attributes to identify them.

Attributes also play an important role in making databases searchable. For example, if we want to find all customers who live in a particular zip code, we can use the customer's address attribute to search for them. Or if we want to find all products that cost less than $10, we can use the product's price attribute to search for them.

In short, attributes are important in DBMS because they help define the data structure in a database. Without attributes, it would be difficult to organize and query data meaningfully. Attributes also help to ensure data accuracy by providing clear definitions for the data being entered into a database. 

Types of Attributes

Let's understand the different types of attributes in DBMS, along with their examples. 

1. Simple Attributes

Simple attributes are those that cannot be further divided into sub-attributes.

For example, A student's roll number of a student or the employee identification number. These attributes are usually assigned by an organization and are used to identify an individual within that organization uniquely. Databases and other systems often use simple attributes to track and manage information.

2. Composite Attributes

Composite attributes are made up of two or more simple attributes. For example, a person's address may be a composite attribute that is made up of the person's street address, city, state, and zip code. Composite attributes can be used to create more complex data models and can be helpful when trying to represent data in a concise way.

3. Single Valued Attributes

Single-valued attributes can only have one value. For example, a person's Social Security Number is a single-valued attribute. Social Security Numbers are used to uniquely identify individuals in the United States and are, therefore, single-valued attributes.

Examples of single-valued attributes include employee numbers, customer numbers, and product codes. Single-valued attributes are typically used to provide a unique identifier for an entity and are often used in databases.

4. Multivalued Attributes

Multivalued attributes can have more than one value. For example, a person may have multiple email addresses or phone numbers. Multivalued attributes in DBMS are often used to store information about relationships between entities. For instance, an employee entity might have a multivalued attribute called "dependents" that stores the names of the employee's dependents. Multivalued attributes can also be used to represent hierarchical data. 

5. Derived Attributes

Derived attributes are based on other attributes and are not stored directly in the database.

For example: Consider a database of employees. Each employee has a date of birth, and we might want to calculate their age. However, age is a derived attribute because it can be determined from the date of birth. As such, it would not make sense to store it directly in the database. Here is an example diagram of a derived attribute in DBMS:

6. Complex Attributes

The complex attribute in DBMS involves both multivalued and composite attributes. For example, someone might have more than one house, and each house might have more than one phone. The phone is then considered a complex attribute.

In the example above, the phone number is a composite attribute of the area code, exchange, and line number. Complex attributes are often used in database design to represent relationships between entities. Here is a complex attribute example explained in the form of a diagram.

7. Key Attributes

DBMS's key attributes are used to uniquely identify each row in a table. Usually, there is more than one key attribute in a table (primary key and foreign key).

For example: In a table of employees, the employee ID would be the primary key, while the manager ID would be the foreign key.

8. Stored Attributes

In a DBMS, stored attributes are the data that remain constant and fixed for an entity instance. These values help in deriving the derived attributes.

For example: consider a customer entity in a bank. The customer's name, age, and address would be stored attributes. The customer's account balance (a derived attribute) could be calculated based on the transactions (another stored attribute) associated with the customer.

So, these are the different attribute types in DBMS and their importance. We believe, by now, you must be intrigued to learn more about the most wanted database in the world. If yes, do consider a MongoDB Administrative Course keywords to get access to 100+ courses and experience 24 hours of instructor training.

Source

Explain the closure of attributes in DBMS

An attribute X's closure is the set of all attributes that depend on X in relation to F. X+ represents what X can determine. 

Algorithm 

Algorithm to compute X+

• Step 1 − X+ =X 
• Step 2 − repeat until X+ does not change 
• For each FD Y->Z in F 
• If Y ⊆ X+ then X+ = X+ U Z 

Example   

Consider a relation R(A,B,C,D,E,F) 

E->A, 
E->D,  
A->C,  
A->D,  
AE->F,  
AG->K. 

Find the closure of E or E+

Solution

The closure of E or E+ is as follows − 

  E+ = E 
=EA   {for E->A add A} 
=EAD  {for E->D add D} 
=EADC {for A->C add C} 
=EADC {for A->D D already added} 
=EADCF{for AE->F add F} 
=EADCF{for AG->K don’t add k AG ⊄ D+)

Difference Between Simple and Composite Attributes in DBMS

Simple and composite are two types of attributes in database management systems.

A simple attribute cannot be further broken down into sub-parts. A composite attribute, on the other hand, is made up of two or simpler attributes. For example, a customer's address might be a composite attribute that consists of the street number, city, state, and zip code.

Composite attributes can themselves be made up of other composite attributes, as in the case of a customer's address, which could be composed of a zip code, streets, etc. However, they can also make data entry and retrieval more complex, as all of the component attributes must be considered when performing these operations.

When defining a database, it is important to understand the difference between simple and composite attributes, as this will affect how the data is structured.   

Conclusion

Attributes are an important part of any database model. In this blog, we looked at the different types of attributes in DBMS and how they can be used in a database system. We also looked at some examples to help you understand the concepts related to entities and attributes in DBMS better.

If you are looking for more information on MongoDB or want to learn how to use it effectively, consider signing up for the KnowledgeHut MongoDB Certification training course. You can learn the art of queries, schema design, CRUD, and data aggregation under the guidance of professionals. The teachers will guide you to write code and build real-world projects along with other related concepts. 

Frequently Asked Questions (FAQs)

1. What is the purpose of attributes in DBMS?

In a database management system (DBMS), an attribute is a database component, for instance, a table. Attributes are used to provide structure and organization within a database, and they can be used to identify and retrieve specific records. 

2. How can database entities and attributes be different?

In a database, an entity type relates to one or more related tables. The attribute is a trait of an entity type describing the entity. For example, the class "Person" would be an entity type, while "Date of Birth" would be an attribute. Entity types tend to correspond to one or more related tables in a database, while attributes typically describe a single aspect of an entity type.

3. How is a multivalued attribute in ER diagram?

An ER diagram represents a multivalued attribute by a double oval. This type of attribute can take on more than one value, which means that it can be used to represent repeating data. For example, a person may have multiple addresses or phone numbers.

4. How do we represent derived attributes in ER diagram?

One way to represent derived attributes in an Entity Relationship (ER) diagram is to include a dashed line from the attribute back to the entity from which it is derived. To sum up, derived attributes are those that can be calculated from other attributes. 

Is an attribute whose values can be calculated from related attribute values?

Is a attribute whose value is dynamic and derived from another attribute?

What are attributes explain different types of attributes?

What is the difference between composite attribute and multivalued attribute?