Data modeling helps in drawing a diagram of data flow in and out of a database. It defines the data format and structure, and also the functions that handle databases and support data flow. While designing a database, the abstract model of the data model you need to build upon is known as the entity-relationship diagram. This is a graphical representation of data requirements in a database. A carefully constructed ERD can be readily converted into a database structure.
Constructing an ERD is a lengthy process. There are three components in designing an ERD. These include entities, attributes, and relationships. While designing a new database from a legacy database, the print ERD feature can be quite effective. It eliminates the need for starting from scratch and constructing a new ERD. This determines the model of the database and forms the justification for the database to exist.
Components Of Entity Relationship Diagram
Let us discuss the three components of ERD, namely – entities, attributes, and relationships.
An entity is the basic object of ERD and it refers to the tables of a database. It may include concepts, roles, locations, things, or events such as students, books, courses, campus, payment, employees, etc. A specific entity in a table is known as an instance, and each instance comes under a different row in a database table.
Relationships are about associations between entities. These are akin to verbs describing the relationships between nouns. Mostly, there are three types of relationships – one to one, one to many, and many to many.
Attributes are descriptions of entities and can be reckoned as adjectives. They eventually become the columns of your database table. For example, if ‘student’ is an entity, its attributes can include name, email, address, phone number, etc. There are two types of attributes – Primary key and Foreign key.
The primary key is a set of attributes uniquely identifying an instance of an entity. For example, if ‘student’ is an entity, the student number is the primary key since this number is unique to every student. This is why the primary key is also known as an identifier. On the other hand, a foreign key is known as a referencing key as it links two tables. A primary key in a table can become a foreign key in another table on executing the print ERD command. Despite this, it remains a primary key in the original table. So, there can be multiple foreign keys in a table.
If you are worried about creating a new database, you can go for shortcuts. There are shortcut options whereby you can print the entity-relationship diagram from the legacy database to the new one and save time and money. Indeed, you can make a new database without writing any code. Just make sure that you are using the right tool.