Our mission is to bring truth back to the internet.Read more →

Last updated on September, 14

Fact checked

2021 Rankings

Best ER Diagram Tools

sub category illustration
Create a seamless structure for your systems and organizations. An ER Diagram tool allows you to organize your company, system, or database in a clear graphical representation. Learn more and try one today!

Frequently Asked Questions on ER Diagram Tools

What is Chen’s ERD Notation style?

Most ER diagram tools have tutorials or templates that you can follow if you don’t know the common symbols. Chen's ERD notation style is still used and considered to be a detailed way to present entities and relationships. Entities are represented by rectangles, attributes are represented by ovals, and relationships are represented by diamonds.

What is the Crow’s Foot Notation?

The Crow’s Foot notation, also known as the Information Engineering style, is also a popular data model. Entities are represented as boxes, and relationships are the lines in between the boxes. The different shapes at the end of these lines represent the cardinality of the relationships.  

What is the conceptual data model?

ER models and data models are typically drawn at up to three levels of detail. The highest-level view is the conceptual data model and contains the least detail. It only shows the overall structure of the model. Only the system architecture is portrayed and does not have a lot of descriptions.

What is the logical data model?

The logical data model is an extension of the conceptual data model and contains more details. This type of model has all the elements used in the actual implementation of the model. It is usually independent of the technology in which it will be implemented.

What is the physical data model?

A physical data model involves all the required properties for the physical implementation of the database. More than one physical model may be derived from a logical model. Physical models must show enough technical detail to be implemented.

What are the limitations of ER diagrams and models?

With ER diagrams, you can only work with relational data. Freely showing you the relationship between data is what ER diagram tools do best. However, if you are working with unstructured data, these tools may not be useful for you. Only some data may be helpful.

What are the different types of entities?

An entity is a group of definable things. There are two categories of entities, namely the weak and strong entities. A strong entity can be defined solely by its own attributes and always has a primary key. Weak entities do not really have enough entities to have a primary key.

What are the different types of entity keys?

Entity keys are attributes that define entities in an entity set. A super key is a set of attributes that define an entity in an entity set together. Candidate keys have the least possible attributes to be a super key. A primary key is used to identify the set uniquely. Lastly, a foreign key identifies the relationships between entities.

What is a surrogate key?

A surrogate key does not have any contextual meaning. It is an artificial key used mainly for data analysis. It may be a substitute for natural keys and is useful when creating queries. Surrogate keys can be used to identify records and good performance uniquely.

What are the different types of attributes?

Attributes are single-valued properties of either an entity-type or a relationship-type. These are classified into simple, composite, derived, or multivalued. Simple attributes mean that the attributive value can no longer be divided further. On the other hand, you can break down a composite attribute to form sub-attributes.Derived attributes are calculated from other attributes present in the database, such as a birth date. It is typically not included in the physical database. Lastly, multivalued attributes can have more than one attribute, such as multiple phone numbers for a person.

What is cardinality?

Cardinality refers to the maximum number of times an instance in one entity can relate to another entity’s cases. The four main cardinalities are the one-to-one, one-to-many, many-to-one, and many-to-many relationships. When viewing cardinalities, it can be shown as same-side or look-across, depending on the symbols.

What are nulls?

A null is a special symbol that is independent of a data type. This does not mean zero. Instead, it means that it is either unknown or not applicable. This is not permitted in primary keys and should be avoided in other attributes. Having nulls can create logical problems when linking relational databases.

What are some tips when using ER diagram tools to create entity relationship diagrams?

Depending on the level needed, show a conceptual, logical, or physical model. Make sure that there are no redundant relationships. If you encounter problems, look for holes in the relationships or find any missing entities or attributes. All entities and relationships should be appropriately labeled.When creating an ER diagram, there are various valid approaches. As long as it shows the necessary information you need, then it’s good. Ensure that the ER diagram tool you are using supports all the data you need to store. If it helps you achieve your goal, you can translate relational databases and ER diagrams back and forth.

Why are the relationships between the entities not showing up?

When importing ERDs, if lines are not showing between your entities, a common occurrence is that your data file does not contain relationships. Ensure that the cells at the end of each row have the right information about the relationships between entities.

What is the difference between ER and EER diagrams?

The ER diagram is a visual representation of data that describes how entities are related to each other in a database. An EER diagram, or an Enhanced Entity Relationship diagram, is an extension of that original entity-relationship model. The EER diagram adds three more concepts, namely, generalization, specialization, and aggregation.

How can I access the source code for ER diagram tools?

Some open-source ER diagram tools provide the link to their code files on their website. From there, you can view the ER diagram tools’ source codes to find and report any issues. If you are a skilled developer, you may also propose some new features, which can be added by the site’s developers.

This site uses cookies. By continuing to use this website, you agree to their use. Read privacy policy for more info.