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Diagrams

Understand Diagrams

On this page

  • Relational View
  • MongoDB View
  • Choose View Mode
  • Color Coding
  • Entity Links
  • Relational and MongoDB View Links
  • Example
  • Relational View
  • MongoDB View
  • New Mapping Rules

This page explains how to interpret diagrams created in the Relational Migrator. Each diagram is comprised of two views, one for your relational database and one for your MongoDB database. The views show the relationships between entities in your databases.

Relational View

In the relational view, each box represents a table in your relational database. The box title indicates the table name.

Each box lists the columns in the corresponding table. For each column, the box indicates the column name and its data type.

Some columns have icons to indicate their role within the table:

  • A key icon indicates the table's primary key.

  • A link icon indicates a foreign key.

MongoDB View

In the MongoDB view, each box represents a collection in your MongoDB database. The box title indicates the collection name.

Each box lists the fields in the corresponding collection. For each field, the box indicates the field name and its data type.

If a collection contains embedded documents or arrays, those fields are shown in-line in the same collection.

Some fields have icons to indicate their role within the table:

  • A key icon indicates the collection's _id field. When you use the wrapped key handling strategy, the _id field contains sub-fields. In this case, the box contains multiple key icons which apply to a single field.

  • A link icon indicates that the field maps to a relational column used in a foreign key.

Choose View Mode

The Relational Migrator provides different view modes for your diagrams: Horizontal Split, Vertical Split, Relational view, and MongoDB view.

View Mode
Description
Horizontal Split
Displays the relational view on top and the MongoDB view is on the bottom. When you create a new project, Horizontal Split is the default view mode.
Vertical Split
Displays the relational view on the left and the MongoDB view on the right.
Relational View
Displays only your relational database diagram.
MongoDB View
Displays only your MongoDB database diagram.

To switch view modes, click a view mode option in the left navigation bar:

View Modes

Color Coding

Entities in the diagram are color-coded based on whether they represent the relational or MongoDB database:

  • Entities with pink highlights are relational tables.

  • Entities with green highlights are MongoDB collections.

Entity Links

The lines between boxes represent the relationships that connect database entities. If two boxes are connected, the corresponding entities are linked with a foreign key. The lines may show the following features of relationships:

  • A small bar across a relationship link indicates a one-to-one relationship between entities.

  • A prong (or "crow's feet") indicates "many" in the relationship.

Relational and MongoDB View Links

When you click a box in either the relational or MongoDB view, the Relational Migrator highlights the corresponding entity in the opposite view. This allows you to see how your relational tables and MongoDB collections are mapped to one another.

Example

The following example shows a sample diagram for a database that tracks orders at a store.

Relational View

This relational view shows the relationship of several tables within a relational database:

Relational Diagram Example

The view shows the following relationships:

  • In the Order table, OrderID is the primary key. CustomerID and OrderStatusID are foreign keys. The Customer and OrderStatus tables contain the references for these foreign keys, respectively.

    • Order to Customer and Order to OrderStatus are both many-to-one relationships:

      • A customer can have multiple orders, and each order only applies to a single customer. In this example, Order is the parent and Customer is the child.

      • An order status can apply to multiple orders, and each order only has a single order status. In this example, Order is the parent and OrderStatus is the child.

  • In the OrderLine table, OrderLineID is the primary key. OrderID and ProductID are foreign keys. The Order and Product tables contain the references for these foreign keys, respectively.

    • OrderLine to Order and OrderLine to Product are both many-to-one relationships:

      • An order line is an individual transaction within an order. An order can have multiple order lines, and each order line applies to a single order. In this example, OrderLine is the parent and Order is the child.

      • A product can apply to multiple order lines, and each order line contains a single product. In this example, OrderLine is the parent and Product is the child.

MongoDB View

This MongoDB view corresponds to the previous Relational view:

MongoDB Diagram Example

The collections and data types presented in the view reflect the mapping rules specified for the project.

The link icons indicate fields which map to a relational column used in a foreign key. For example, in the Order collection, the OrderStatusID field represents a foreign key that links the Order and OrderStatus tables.

New Mapping Rules

The following new mapping rules have been created to better utilize MongoDB's embedded data model:

  • The Order collection contains a rule that maps OrderLines as an Embedded array. The OrderLine table from the relational schema is mapped as an array of objects inside the Order documents, using the foreign key relationship from the relational schema.

    Order Mapping Rule Example

  • The Customer collection contains a rule which maps Orders as an Embedded array. The Order table from the relational schema is mapped as an array of objects inside the Customer documents, using the foreign key relationship from the relational schema.

    Customer Mapping Rule Example

Both of the preceding mapping rules remove the ID fields from the mapping. Since the OrderLines and Orders fields are embedded in their parent fields rather than being referenced with a foreign key, the ID fields are not required to link the fields together.

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