Hi Thomas Adam
Hence the "Class" table would be the master, and "Classification" the detail. "Class" would therefore have:
classId (Primary Key) classification (varchar (255))
and "classification":
classfnId (primary Key) classId (foreign key) classfn_name (varchar (255))
Using referential integrity from within postgres (via SQL), it's then a smatter of linking child --> master. So yes, it's certainly possible to do.
I've implemented tables class & classification with this design, which you will see if you connect again. (The previous 'look-up' tables are still also there for now.) I've put a bit of data into them. A problem I have with this design, which maybe somebody can give a solution to is this: I now want to say what ethnic group students belong to, and so on, so I need a table like (apologies for word-wrap): create table student_classification( student_classification_id integer unique, student_id integer constraint references student(student_id), classification_id integer constraint references classification(classification_id) ) However, a student belongs falls into at most 1 ethnic group. Therefore I need a constraint on the table to prevent the entry of two records where the same student is assigned 2 classification_id's which actually belong to the same class (ie class_id=2 , Ethnic). A table constraint won't do, as two tables are involved. regards Richard -- richard@tortoise.demon.co.uk