Information Technology Reference
In-Depth Information
major
student-no
Course
Student
Cours-no Cours-name
CS101
CS201
IS301
course-taken
(Stored OID)
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Major
Student
Intro to CS
Database
Intro to MIS
123
124
Computer Science
Information Sys
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name
.
OID
Cours-register
Cours-no
Studen-no
course-
register
Course
CS101
CS201
IS101
123
123
124
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mapping
OID
SQL Query Graph
OSQL Query Graph
Fig. 5.12 A SQL query graph (QG) is mapped to an OSQL QG
Refer to the case study for an example.
Relational Operation Insertion
Attribute values are specified for a tuple to be inserted in a relation R k . We denote
by v 1 , v 2 , … v n the values corresponding to attributes in R k and, if any, with V f1 ,
V f2 , … V fm corresponding to the foreign keys in R k . The transformation technique
is to preserve the referential integrity between parent relations and child relations
through foreign keys V f1 , V f2 , … V fm in RDB to the association between class C k
and its associated class through aggregate attributes P c1 , P c2 , … P cm in OODB as fol-
lows (Zang and Fong 2000 ):
Step 1. Locate the to-be-inserted object
According to the pre-process, we can map the to-be-inserted tuple in RDB to a
corresponding to-be-inserted object in OODB as follows:
SQL: INSERT into R (v 1 , v 2 …v n , V f1 , V f2 …V fm ) value (V(v 1 ), ..V(v n ),
V(V f1 )…V(V fm )
Pre-process(schema translation): Relation R k (v 1 ,v 2 …v n ,V f1 ,V f2 …V fm )
Class C k (A 1 , A 2 …A n , P c1 , P c2 …P cm )
Step 2. (optional). Locate composite objects that contain the to-be-inserted object.
The aggregate attributes of a composite object contains the stored OID of an-
other object. We can locate, if any, the parent relations R p1 , R p2 , … R pm of the rela-
tion R k with the to-be-inserted tuple by matching its foreign keys V f1 , V f2 , … V fm
against their parent relations' primary keys. We can map these parent relations to the
associated class C a1 , C a2 , … C am class of the to-be-inserted class C k by matching the
values of foreign keys as follows:
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