Relation notations

Last modified: June 2, 2025

Foreign key relations are displayed as lines connecting tables. The relation appearance depends on the selected notation. dbForge Studio supports IE and IDEF1X notations for the diagrams.

IDEF1X notation

IDEF1X (Integration Definition for Information Modeling) is a modeling language for developing a logical data model.

Identifying relations, i.e., relations where all foreign key columns are included in the primary key of the child table, are displayed as continuous lines with a black circle on the child end. See the following example.

Non-identifying relations are displayed as dotted lines with a black circle on the child end. If this relation is an Optional Non-Identifying Relationship (child foreign key columns are nullable), a white diamond is displayed on the parent end of the relation. See the following examples.

The letter Z at the child end of the relationship appears if there can be only zero or one child record. It depends on whether the foreign key columns in the child table are unique (belong to the primary key or unique index). Thus, identifying relations are always displayed with the letter Z. Non-identifying relations can be displayed both with or without the letter Z.

IE notation

IE notation is used by default. Relations are displayed as continuous lines. The ends of the lines depend on relation cardinality. Relation cardinality is determined automatically from the foreign key constraint; it cannot be specified by the user (except for editing child table constraints).

In Microsoft SQL Server, one record of the child table corresponds to 0..1 (zero or one) or 1 (exactly one) record from the parent table. It depends on the NOT NULL constraints on the foreign key columns in the child table.

One record of the parent table corresponds to 0..1 (zero or one) or 0..N (zero, one, or more) records from the child table. It depends on whether the foreign key columns in the child table are unique (belong to the primary key or unique index).

Parent record	Child record	Example
1 (exactly one)	0..N (zero, one, or more)
1 (exactly one)	0..1 (zero or one)
0..1 (zero or one)	0..N (zero, one, or more)
0..1 (zero or one)	0..1 (zero or one)