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Relationship Editing

Relationships are drawn from the canvas context menu or with a shortcut — see Editing Start.
This page covers what you can do with one once it exists.

Deletion​

Possible to delete via the relationship context menu.

Relationship context menu with delete

There is no shortcut for it, because a relationship is not selected the way a table or a memo is.
Relationships are also removed together with what they connect: deleting a table removes every relationship touching it, and deleting a column removes every relationship that uses it.

Type Change​

Change available through the relationship context menu.
Four types are offered, and the current one is marked with a check:

  • Zero One
  • Zero N
  • One Only
  • One N
Relationship type menu

These are the same four types you start a relationship with, each with its own shortcut — see Editing Start.

N:M Relationships​

Because the editor is based on the physical model, an N:M relationship is expressed with a mapping table, as shown below.

N:M relationship result

Importing GraphQL, DBML, or AML builds the mapping table for you.
A many-to-many declaration arrives as a table named <left>_<right>, commented Junction table inferred from <left> <-> <right>, joined to both sides by identifying relationships.
See Importing or Exporting Files.

Identifying Relationships​

Drawing a relationship copies each primary key of the parent table onto the child table as a NOT NULL foreign key column, so a new relationship starts out non-identifying.
To make it identifying, set those foreign key columns on the child table as primary keys with Alt + K or Primary Key in the table context menu.

Identifying relationship

The editor keeps this in step on its own.
A relationship is identifying while every column on its child side is a primary key, and turns non-identifying as soon as one of them is not.

Reading a Connector​

  • An identifying relationship is drawn as a solid line, a non-identifying one as a dashed line.
  • The child end carries the cardinality symbol of the relationship type: a ring and a bar for Zero One, a ring and a crow's foot for Zero N, two bars for One Only, and a bar and a crow's foot for One N.
  • The parent end is a ring when any of the foreign key columns allows NULL, and a short dash when they are all NOT NULL.
  • Hovering a connector highlights it along with the columns it links in both tables.

Hide connectors entirely with the Relationship view option — see Table-related Functions.

Connector Routing​

Connectors are routed orthogonally.
A route bends around the tables that sit between its two ends instead of crossing them, and its corners are cut at 45 degrees.
Routes leaving the same side of a table are spread onto separate corridors so they do not run down one another.

There is nothing to configure.
Routes are recalculated automatically whenever anything on the canvas moves or resizes, so they never need touching by hand.