Frequently Asked Questions › Implied Relationships

Implied Relationships

Question: Can I detect relationships that are not defined using the Foreign Key mechanism?

Answer: Yes. CA ERwin DMV will infer implied relationships, based on same name attributes. For example, if in table CLIENT there is a PK based on column Cli_ID and in the ORDERS table there is a non-key column attribute Cli_ID, CA ERwin DMV will detect this relationship as being a one-to-many (1:N) from CLIENT to ORDERS. It is a 1:N because on the CLIENT side the column is unique (it is a PK) and on the ORDERS side the column is non-unique (non-key attribute).

Question: If I do not have a good naming convention how can I take advantage of the implied relationships detection?

Answer: CA ERwin DMV allows you to define synonyms for the attributes. If in one table you use column Cli_ID and in another table Cli#, you can define these as synonyms. Go to User Definitions and select Synonyms. This way CA ERwin DMV will consider these two as the same.

Question: What do I have to do to make CA ERwin DMV detect implied relationships?

Answer: CA ERwin DMV is installed with the implied relationship detection as a default. If you want to change this setting, go to Tools, Preferences, and Model Settings and select the proper option for Relationship Processing. The option Foreign Keys Only indicates that no implied relationships will be detected. The option ALL indicates that implied relationships will be detected.

Question: Do I have any overhead using implied relationships?

Answer: There is always some overhead detecting implied relationships, but this is only noticeable in very large models. CA ERwin DMV must compare every attribute in every table with the attributes in every other table.