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Matakuliah
Tahun
: M0264/Manajemen Basis Data
: 2008
Manajemen Basis Data
Pertemuan
Objectives
• The System Catalog (Sistem Katalog)
• Overview of Query Processing (Pengenalan Evaluasi
Operator)
• Algorithm for Relational Operation (Logika Operasi
Relasi)
• Introduction to Query Optimization (Pengenalan Query
Optimization)
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The System Catalog
• Catalog Tables / Data Dictionary
• Informasi in Katalog :
 Tabel
 Index
 View
• How Catalogs are stored
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Overview of Query Processing
Activities involved in retrieving data from the database.
• Aims of QP:
– transform query written in high-level language (e.g. SQL), into
correct and efficient execution strategy expressed in low-level
language (implementing RA);
– execute strategy to retrieve required data.
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Overview of Query Processing
• Phases of Query Processing
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Algorithm for Relational Operation
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Selection ( ) Selects a subset of rows from relation.
Projection ( ) Deletes unwanted columns from
relation.
Join (
) Allows us to combine two relations.
Set-difference ( ) Tuples in reln. 1, but not in reln. 2.
Union ( ) Tuples in reln. 1 and in reln. 2.
Aggregation (SUM, MIN, etc.) and GROUP BY
Introduction to Query Optimization
Activity of choosing an efficient execution strategy for processing
query.
• As there are many equivalent transformations of same high-level
query, aim of QO is to choose one that minimizes resource usage.
• Generally, reduce total execution time of query.
• May also reduce response time of query.
• Problem computationally intractable with large number of relations,
so strategy adopted is reduced to finding near optimum solution.
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Introduction to Query Optimization
• Query
• Query Parser
• Query Optimizer
 Plan Generator
 Plan Cost Estimator
• Catalog Manager
• Query Plan Evaluator
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Introduction to Query Optimization
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