Matakuliah
Tahun
Versi
: M0174/OBJECT ORIENTED DATABASE
: 2005
: 1/0
Pertemuan 16
Object Query Language (Lanjutan
bagian 3)
1
Learning Outcomes
Pada akhir pertemuan ini, diharapkan mahasiswa
akan mampu :
• Mahasiswa dapat Menghasilkan query
language dalam object data model (C3)
2
Outline Materi
•
•
•
•
•
Retrieving
Creating structured
Creating mutable
Creating collections
Conversion
3
Retrieving
• Definition
• Example
– Return the existing Product object with the
object name, best_seller
best_seller
– Return a string literal, which is the value of the
name attribute of the product object called
best_seller
best_seller.name
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Retrieving
– Return a collection-object which contains the
existing mutable product object for the bat
bike product
select p
from products p
where p.name = “bat bike”;
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Retrieving
– Return a literal collection-object containing
string literals which are the values of the
colour attribute of mutable product object
select p.colour
from products p
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Creating structured
• Structured-literal (set, bag, list, array, and
structure-literal) can be created using the
object constructor operators, struct, set,
bag, list, and array
• Example
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Creating structured
<query> ::= struct ([<identifier> : <query>
[,<identifier> : <query>] *] ) |
set ([<query> [,<query> *] )|
bag ([<query> [,<query> *] )|
list ([<query> [,<query> *] )|
array ([<query> [,<query> *] )
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Creating mutable
• Type names are used as constructor
operators to create new mutable objects of
the specified type
• Example
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Creating collections
• The select…from…where form of OQL has
number of variations which can be used to
return different types of collection object
– The general form
– The distinct
– The group by
– An order by
• Example
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Conversion
•
•
•
•
•
Listtoset
Distinct
Element
Flatten
Example
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SUMMARY
• OQL can retrieve existing objects and can
also create new ones
• New objects can be created using the
constructors, set, bag, list, array, and
struct
• OQL also includes operators for changing
the type of an object (listtoset,
distinct,element, and flatten)
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