Foundations of Relational Implementation (1) IS 240 – Database Management Lecture #13 –...

Foundations of Relational

Implementation (1)

IS 240 – Database ManagementLecture #13 – 2004-04-01

Prof. M. E. Kabay, PhD, CISSP

Norwich University

mkabay@norwich.edu

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Topics

Review of Relational TerminologyDefine DB Using DDLAllocate Disk SpacePlan for MaintenanceLoading the DBDML Interfaces

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Review of Relational Terminology

Relation / table / file / datasetTuple / row / record / entryAttribute / column / fieldDomainUniqueness

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Key – Two Meanings

Design: unique identifier(s) of row Implementation: performance toolLogical key: unique identifierPhysical key: column with an index for faster

performance

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Indexes

Kroenke reserves word “key” for logical keyUses word “index” for physical key Indexes are useful

Find rows fastRetrieve rows in a sorted orderEnforce uniqueness

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Example of Indexes in a Database

Compare # I/Os required to read all the order #9890Without

indexWith index

on OrdNoWith

packing* on index

OrdNo OrderData OrdNo OrderData9890 … 343 …7882 … 343 …7572 … 967 …5308 … 3072 …5308 … 4502 …8021 … 5308 …8496 … 5308 …9394 … 5308 …3072 … 7572 …7882 … 7882 …9890 … 7882 …5308 … 8021 …4502 … 8021 …8021 … 8496 …9890 … 9394 …967 … 9836 …343 … 9890 …343 … 9890 …9836 … 9890 …

*

1 b

lock

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Implementing RDB

Having designed a DB using the relational model, there’s no problem in defining a DB using today’s DBMS products

Use the Data Definition Language (DDL) of the DBMSFormalized language for describing what

we needVaries a bit from DBMS to DBMSEasy to learn once you’re mastered any

one of them

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Define DB Using DDL

Text-file (schema) DDLSpecific syntaxName all the elementsName all the tablesName all the indexes and links

Graphical systemsMS-Access uses tables and also graphicsEasy to define details using textStructures can be linked using graphicsMenus provide guidance, limits

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Allocate Disk Space

PC-based products generally allocate space dynamicallyDB grows as neededDon’t have to worry about defining

maximum sizeMainframe / server DBs generally require size

definitionsNeed to reserve space in advancePerformance issues become important

Multiple disk drives or controllersTry to avoid thrashing of disk heads

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DB Performance Issues

Computer system performance always depends on 5 factorsAccess to & speed of CPUAccess to & speed of RAMAmount & speed of disk I/OCommunications speedApplication design

DB performance often affected byPresence / absence of indexesGood / bad packing of recordsLocking strategies (coming in later lecture)

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Plan for Maintenance

Databases often central components of production systems

Plan forBackupsDiagnostics to find corrupted data

Child records without parentsRecord counters that are incorrectPointers to non-existent recordsData that violate business rules

Archiving inactive recordsCompaction of data files

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Loading the DB

Have to get data somewhereMost DBs get historical data

Older DBsSpecial programs written to read old DB,

write into new DB with correct formatOften get exceptions – write to exception

fileMay have large-scale data entry from paper

records – need careful verificationSome critical systems use dual data entry

Compare records

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Types of Data Manipulation Languages (DMLs)Relational algebraRelational calculusTransform-oriented languagesGraphical interfaces

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Relational Algebra

Operators function on recordsUnion / intersection etc.

Much like set theoryProcedural language

Step-by-step changes in collections of dataNot used in commercial DBsUseful to understand as preparation for SQLWill study in next lesson

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Relational Calculus

Non-procedural theoretical framework for dealing with relations

E.g., De Morgan's law, “The complement of a union is equal to the union of the complements."

Learned in mathematics and advanced theory of programming and data structures

Not used in commercial DB processingNot part of this course

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Transform-Oriented Languages

Non-proceduralChange relations into a single relationThus define conditions for selecting records

and end up with a set of records that satisfy the conditions

SQL is most important example of this kind of language

Will study in detail in this course

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Graphical Interfaces (1)

Query-by-Example (QBE)

User sees place to enter specific values or rangesGenerates SQL without bothering user

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Graphical Interfaces (2)

Query-by-Form (QBF)Allows more complex queriesStill generates underlying SQL

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DML Interfaces to the DBMS

Forms (e.g., in MS-Access)Query languages (e.g., SQL)Stored procedures (incl. triggers)API = application program interface

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Homework

For Thu 8 April 2004: REQUIREDReread chapter 8, pp. 211-221 thoroughly

using Read-Recite-Review phases of SQ3RDo exercises 8.1-8.17 for 34 points

For next Tuesday:Read onwards in chapter 8 from page 221

through 231Continue working on MS-Access lab work

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DISCUSSION