When right clicking on a table in the Schema Browser and choosing to open in the Entity Relationship Diagramme, only one tables comes up. Two or more tables are expected since the tables are related based on different columns.
For example, COURSE.Course_id is related to ENROLLED.Cid on a 1:many relationship. But when bringing COURSE table into the ERD, only that table is opened and ENROLLED is not brought up as expected.
Relationships need to be built within the table design with constraints and keys. If there are no keys set up between tables then Toad's ERD will not pick up any relationship between them.
Set up key relationships between the related columns so that Toad's ERD will bring up all related tables and show dependencies.
For example, set COURSE.Course_id as the primary key and ENROLLED.Cid as the foreign key to Course_id.
To add these key constraints to an existing table:
1. Go to the table in schema browser and select alter table for the table in question.
2. Go to the constraints tab and choose to add constraints.
3. Select the type of constraint and select the column to use.
4. If setting up a foreign key, please select a reference table that has been set with a primary key.
5. Click OK at the bottom right corner to run the alter table script.