For MySQL its not possible to set a relationship as 1:1. Only 1:N is possible with other DBMS, e.g. Oracle, it is possible to have 1:1 why not with MySQL? Regardsless whether Identifying or Non-identifying, Mandatory or Optional: the field with the "N" is always grayed out, so I cannot replace it with a "1".
Please see the TDM manual. On page 21 the following is written:
*** Defining Cardinality
If you need to set up a relationship as 1:5, for example, define the cardinality at the bottom of the Edit Relationship dialog. An appropriate number will be displayed near the end point of the selected relationship line. Note: this feature is available only for target databases which support triggers. See some of the currently supported databases:
In Toad Data Modeler, you can generate referential integrity declaratively or via triggers. If you want to generate cardinality, you must generate the referential integrity rules via triggers, not declaratively. ***
The above mentioned note �This feature is available only for target databases which support triggers� explains the issue with MySQL. As far as I know the triggers are suported in MySQL 5, but not in all versions. That�s the reason why you cannot define cardinality in TDM.
The last sentence �If you want to generate cardinality, you must generate the referential integrity rules via triggers, not declaratively.� explains the issue with Oracle. You will see the difference only if you generate the RI via triggers, not declaratively.