SqlDBM allows using both IDEF1X and Crow's foot notation for physical and logical (virtual) relationships. To apply a notation style, go to the Notation section of the diagram properties in Diagram Explorer or call the context menu on any relationship.

Figure 1. Relationship Notation on Diagram

IDEF1X notation

By default, projects use IdeF1X notation.

Solid lines represent identifying relationships and dashed lines represent non-identifying relationships. In a non-identifying relationship, the foreign key field does not form a part of the parent table's primary key.

Null-able foreign keys can also be specified in the properties and are represented by a diamond next to the child table.

Figure 2. Relationship Notation on Diagram

Crow’s (or Martin) foot notation

SqlDBM also supports Crow's foot notation so that users can track cardinality between tables.

In comparison with IDEF1X notation, relationships in Crow's foot notation always have solid lines.

Figure 3. Relationship Notation on Diagram

The following symbols are used to represent cardinality:

Ring : "zero"
Dash : "one"
Crow's foot : "many"

Child table

These symbols are used in pairs to represent the four types of cardinality that a child entity may have. The inner component of the notation represents the minimum, and the outer component represents the maximum.

Ring and Crow's Foot → minimum zero, maximum many (optional)
Ring → minimum zero, maximum one (optional)
Dash → minimum one, maximum one (mandatory)
Dash and Crow's foot → minimum one, maximum many (mandatory)

Use radio buttons in the "Cardinality" tab from relationship properties to set it

Figure 4. Relationship Notation on Diagram

By default, "From zero to many" is selected.

Parent table

Parent table may have two types of cardinality:

Ring → minimum zero, maximum one (optional)
Dash → minimum one, maximum one (mandatory)

Mark "Allow null" in relationship properties to represent "From zero to one" when "from one to one" is chosen. Notice, "Allow null" option is available for entities with PK columns only.