The vertical toolbar on the left side of an EER Diagram has six foreign key tools:
one-to-one non-identifying relationship
one-to-many non-identifying relationship
one-to-one identifying relationship
one-to-many identifying relationship
many-to-many identifying relationship
Place a Relationship Using Existing Columns
An identifying relationship is one where the child table cannot be uniquely identified without its parent. Typically this occurs where an intermediary table is created to resolve a many-to-many relationship. In such cases, the primary key is usually a composite key made up of the primary keys from the two original tables. An identifying relationship is indicated by a solid line between the tables and a nonidentifying relationship is indicated by a broken line.
Create or drag and drop the tables that you wish to connect.
Ensure that there is a primary key in the table that will be on
the “one” side of the relationship. Click on the
appropriate tool for the type of relationship you wish to create.
If you are creating a one-to-many relationship, first click the
table that is on the “many” side of the relationship,
then on the table containing the referenced key. This creates a
column in the table on the many side of the relationship. The
default name of this column is
table_name_key_name where the table
name and the key name both refer to the table containing the
When the many-to-many tool is active, double-clicking a table creates an associative table with a many-to-many relationship. For this tool to function there must be a primary key defined in the initial table.
Use the Model menu, Menu Options menu item to set a project-specific default name for the foreign key column (see Section 220.127.116.11.5.4, “The Relationship Notation Submenu”). To change the global default, see Section 3.2.4, “Modeling Preferences”.
To edit the properties of a foreign key, double-click anywhere on the connection line that joins the two tables. This opens the relationship editor.
Mousing over a relationship connector highlights the connector and
the related keys as shown in the following figure. The
film and the
tables are related on the
film_id field and
these fields are highlighted in both tables. Since the
film_id field is part of the primary key in the
film_actor table, a solid line is used for the
connector between the two tables. After mousing over a
relationship for a second, a yellow box is displayed that provides
If the placement of a connection's caption is not suitable, you
can change its position by dragging it to a different location. If
you have set a secondary caption, its position can also be
changed. For more information about secondary captions, see
Section 18.104.22.168, “Connection Properties”. Where the notation
Classic for example, the
cardinality indicators can also be repositioned.
The relationship notation style in Figure 8.10, “The Relationship Connector” is the default, crow's foot. You can change this if you are using a commercial version of MySQL Workbench. For more information, see Section 22.214.171.124.5.4, “The Relationship Notation Submenu”.
You can select multiple connections by holding down the Control key as you click a connection. This can be useful for highlighting specific relationships on an EER diagram.