Toad changes the data type value or length when using foreign key in relationship.
For example:
TableA with PAT_ID Varchar(12) - Primary Key
TableB with PAT_ID Varchar(18) - Child Key
When clicking on the Relationship icon and then connecting the two tables in the modeling area,
TDM will created “another” PAT_ID column as Varchar(12).
Double-click the connector line to open the Relationship Properties window. Under the Child column in the Relationship Properties window, click on the drop-down list and then chooses the “other” PAT_ID in there. This “other” PAT_ID is the original PAT_ID Varchar(18) column. At this point, TDM automatically changed it from Varchar(18) to Varchar(12).
This behavior is the correct behavior for connecting two entities with defining relationship and linking the two attributes this way. The Data type must match by design.
The data type in both the parent and child attribute must comply based on referential integrity between parent and child. Even when the data type stays the same, all the type's values, attributes must match, just like the Varchar length example mentioned above.
