Matakuliah
Tahun
Versi
: M0174/OBJECT ORIENTED DATABASE
: 2005
: 1/0
Pertemuan 14
Object Query Language (Lanjutan
bagian 1)
1
Learning Outcomes
Pada akhir pertemuan ini, diharapkan mahasiswa
akan mampu :
• Mahasiswa dapat Menghasilkan query
language dalam object data model (C3)
2
Outline Materi
•
•
•
•
•
Selecting objects from a collection
Complex test an objects
Arithmetic comparisons
Tests on collections
String matching
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Selecting objects from a collection
• The general form of this type of OQL query
is
Select <variable>
From <collection-object><variable>
Where <restrict-predicate>
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Selecting objects from a collection
• Selecting objects from more than one collection
– Union
– Intersect
– Except
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Complex test an objects
• The rules for evaluating a Boolean
expression constructed using and, or, not,
are:
– An expression is evaluated form left to right
– Sub expressions in brackets are evaluated
first
– Not are evaluated before “and” and “or”.
6
Arithmetic comparisons
•
•
•
•
•
•
= (equal)
!= (not equal to)
> (greater than)
>= (greater than or equal to
< (less than)
<= (less than or equal to
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Tests on collections
• OQL Boolean expressions can test the
membership of collection objects as in the
object algebra. The following comparison
can be made:
– For all
– Exist
– Unique
– In
– Some, any, all
– Set inclusion
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String matching
• String matching can be used to select
objects on the basis of textual properties,
such as names or decriptions
• ?
• * or %
• Example
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String matching
• Accessing Object in a List or an Array
– Accessing object in a list or an array can be
done in the following way:
• First, Last
• Access by index
• List or Array addition
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String matching
• Grouping objects
• Example
Select *
From products p
Group by colour:p.colour
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SUMMARY
• Objects are selected from a collection
using the SQL-like select…from…where
form of query
• The form clause specifies which collection
is to be searched, and the where clause
specifies the condition for selecting an
object
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