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Pertemuan 16Object Query Language (Lanjutan bagian

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Matakuliah : M0174/OBJECT ORIENTED DATABASE

Tahun : 2005

Versi : 1/0

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Learning Outcomes

Pada akhir pertemuan ini, diharapkan mahasiswa

akan mampu :

• Mahasiswa dapat Menghasilkan query language dalam object data model (C3)

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Outline Materi

• Retrieving

• Creating structured

• Creating mutable

• Creating collections

• Conversion

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Retrieving

• Definition

• Example– Return the existing Product object with the

object name, best_sellerbest_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)