Datamodel diagram

what are the relationships we specify in datamodel diagram? And also i have one doubt I have three tables

Table A (emp Id(pk) ,name) Table B (empId(pkfk),depno(pk),department) Table C -( contain department list in office)

In Table B creation I referred Fk as empid.so that i开发者_JS百科 drawn relationship between Table A and TableB.But in TableB department be a a dropdown list it contained list of departments from Table c.Is it necessary to specify the relationship between table b And c in hierarchy datamodel.

Basically you specify the relations between the tables of your datamodel.

For more on this:

Entity relationship model

Data model

Relational model