DbView Database visualization

Joins

A join is associated to a foreign key. It represents a relation between two fields : The "reference" field and the "dependent" field.

The dependent field is the field that declares the foreign key (which can be hard or soft).
The reference field is a field to which the dependent field is associated.

We could say that: The value of the dependent field depends on the value of its associated reference (field).

A join is associated to cardinalities.

Graphically, a join is represented by an arrow with a 4-column grid in the middle of it. The start of the arrow is the dependent table. The end of the arrow is the reference table.

Example for a soft foreign key:

dbview.sh export -exporter dot-full -zoom sfk_dependent,sfk_reference -db-daptor mysql -host localhost -user root -password root -dbname mydb -port 8889 -fkmatcher fk-us-target-table-name -layout v > graph.dot

dot -Tgif -Ograph graph.dot

Example for a hard foreign key:

dbview.sh export -exporter dot-full -zoom hfk_dependent,hfk_reference -db-daptor mysql -host localhost -user root -password root -dbname mydb -port 8889 -fkmatcher fk-us-target-table-name -layout v > graph.dot

dot -Tgif -Ograph graph.dot

Starting from the left column of the join's grid, we find:

The cardinality of the association between one dependent record and some reference records (see cardinalities).
The name of the dependent field, in the dependent table.
The name of the reference field, in the reference table.
The cardinality of the association between one reference record and some dependent records (see cardinalities).

Plase note that joins are not always visible on graphical representations. It depends on the export used to generate the graphical representation of the database.