Data Conversion - Information Systems Reengineering, Integration and Normalization - page 164

ClassEnrol
attr year integer
attr grade: string
association attr register ref graduate_student
association attr provide ref section
end

Step 2—Unload data into sequential files.
By applying the algorithm specified, this step unloads data from each relation
into a sequential file along with its association data from other relations.
The idea is to load the attribute data from the input relation, and the association
attribute data from the loaded object-oriented database. The Select statement is to
retrieve class occurrences that have been loaded into the object-oriented database
with the stored OID. The association attributes are in italic.
For implementation, a foreign key will be loaded with referred data using the
stored OID. The insert and select statements in the following are from a prototype
written using UniSQL (UniSQL 1993 ).
The content of file F i after the first substep in unload process are the following
insert statements:

insert into student (student#, student_name, sex) values

('012888', 'Paul Chitson', 'M')

insert into student (student#, student_name, sex) values

('120008', 'Irene Kwan', 'F')

insert into student (student#, student_name, sex) values

('117402', 'John Lee', 'M')

insert into graduate_student (student#, degree_to_be, register )
values ('012888', 'M.Sc.', null)

insert into graduate_student (student#, degree_to_be, register )
values ('120008', 'Ph.D.', null)

insert into section (section#, lecture_hour, taught_by, divide,
provide ) values (1, 30, null, null , null )

insert into section (section#, lecture_hour, taught_by, divide,
provide ) values (2, 30, null, null, null )

insert into enrol (year, grade, register_by , provide_by ) values

(1995, 'A', null, null )

hinsert into enrol (year, grade, register_by, provide_by ) values
(1996, 'B', null, null )

insert into instructor (inst_name, ss#, inst_addr) values

('A.B.Adams', 415223641, 'White Plains')