Entity Relationship Diagram - ERD

Introduction

An Entity Relationship (ER) Diagram is a visual representation that functions as a flowchart, illustrating the relationships between various "entities" within a system. These entities can represent people, objects, or concepts. In the context of our application, the ER Diagram serves as a powerful tool for elucidating the interconnections between different datasets and their corresponding columns. By offering a clear and structured overview, it enables users to comprehend how one dataset relates to another, thereby facilitating a more profound understanding of the overall data. This article explains how an ER diagram can be used in a better understanding of the data.

Data Model Tab

ER diagram is located on the detail page of any table under the "Data Model" tab. 

Within the ER diagram, you'll encounter one prominently featured table, and The other tables linked to this central table are connected through arrows, indicating their relationships.

By default, you'll see the name of each table displayed. However, for more comprehensive information, there's an option to expand each table, revealing the specific columns contained within.

On the left of the ER diagram, there are some interactions which are:

1. Zoom In
2. Zoom Out
3. Fit View
4. Toggle Interactivity

Users can adjust the diagram's zoom level according to their needs. This can be achieved by either using the mouse scroll along with the CTRL button or simply through zoom controls. To navigate the diagram, users can right-click and drag their mouse to pan the view in different directions.

The "Fit View" option instantly resets the ER diagram to its default fit view on the screen.

This function serves to enable or disable various interactions within the ER diagram. For instance, when the toggle interactivity is in the locked state, users cannot add relations or access reference views of columns in the ER diagram.

Add/Edit Relationships

Before moving to adding or editing the relationships let us define the three basic relations that exist in the application:

1. Relationship added from Database
2. Relationship recommended by DvSum
3. Relationship added by User

Every relationship has a reference view and it can be opened by simply clicking on the line that connects the two tables

• The Relationship that is added to the database can neither be edited nor deleted. 

• The second type of relationship is the one that is recommended by DvSum. These relationships can be edited or deleted. There is another option of "Confirm" along with the "Edit". Once the user confirms the relationship this relationship is changed to the "User added" relationship type.

• The "User added" relationship is the third type of relationship. One way of making the relationship "User added" is just confirming the relationship which is recommended by DvSum:

Another method to create a "User-added" relationship is by manually adding and defining the relationship. To add a relationship, click on the "+" icon located in the top-right corner of the source table. This icon allows users to initiate the process of adding a new relationship.

Once the "+" icon is clicked the "Add Relationship" reference view is opened. Here the Source table is mentioned, Users can add the Reference table from the drop-down menu and define any type of relationship

After adding the Reference table and selecting the Relationship type the user will be required to add source fields and reference fields for which the relationship is being added. Users can add single or multiple columns for the relationship.

Note: It is to be noted that once any column is added to a relationship then that column can not be added again, the column will be greyed out when a user tries to add it to the relationship:

Once the relevant fields are added user can click on "Save Changes" and the relationship will be created. In this way, the user can add multiple relationships to the source table. The relationship that is added by the user can be edited again by clicking on the line connecting the tables. If the relationship is not required then it can be removed also:

Setting Tables as Context

On the ER diagram other than the source table there is an arrow icon on the other tables on the top right. 

When this button is clicked the detail page of the respective table is opened and the Data Model Tab is shown:

Grid View 

By default, the view which is opened is the Model view of the "Data Model" tab. Along with the model view, there is another view "Grid View" which basically shows all the relationships defined in the ER diagram and some other information. The relationships that are recommended by DvSum or user-added can also be edited/deleted from here.

Levels in ERD

There are levels defined in the ER diagram. On level 1 the tables that are directly related to the source table are shown:

Moving to Level 2, you'll discover the tables associated with tables on Level 1.

In the same way, the tables that are further related to the highlighted tables will be shown in the 3rd+ level thus showing the ER diagram in detail.