Sem 1 2002 10 / 1 Course Review We’ve made it to Lecture 10 This is the last lecture in the Course...

Sem 1 2002 10 / 1

Course ReviewCourse Review

We’ve made it to Lecture 10

This is the last lecture in the Course CO24

Sem 1 2002 10 / 2

Lecture 10 - Review of Subject MaterialLecture 10 - Review of Subject MaterialLecture 10 - Review of Subject MaterialLecture 10 - Review of Subject Material

This is the final lecture for Semester 1, 2002

I will introduce the major components of a Database Management System as a means of reviewing much of the material

Then we will move onto a slightly wider subject review

Sem 1 2002 10 / 3

Sem 1 2002 10 / 4

Some final thoughts on SQLSome final thoughts on SQL

IBM’s DB2 is overtaking Oracle’s DBMS 8.0.n and 8i as the DBMS of the period.

An SQL analyst who also is a member of X3H2, a committee set up to determine amendments and extensions to SQL and which then become ANSI standard (if they are approved etc.), was asked why this migration and customer redirection was occurring. His name is Joe Celko.

Sem 1 2002 10 / 5

Some final thoughts on SQLSome final thoughts on SQL

His comments ?

DB2 products are now more uniform across their platforms.

This means that the same database occurs at all levels in a company

Oracle runs on many platforms but is retrofitted and not designed from the start for that niche.

DB2 has a better Optimiser and other internals (read indexing and join functions)

Sem 1 2002 10 / 6

Course ReviewCourse Review

• We will look briefly at the material covered in the preceding lectures

• Introduce some more material on SQL

• and have a few thoughts about the examination

Sem 1 2002 10 / 7

Introduction to SQL, Database DesignIntroduction to SQL, Database DesignIntroduction to SQL, Database DesignIntroduction to SQL, Database Design

• Data, Information, Need for Information

• Database, Database Management Systems

• Commercial Models - Hierarchical, Network, Relational

• Business Activities, Functions, Processes

• Need for Information to Manage Resources

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• Need for Information to be– Accurate, Representative, Timely, Adequately Based,

– Protected against Loss, Corruption, Unauthorised Access

• Communication capabilities

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• Designing a database

– User requirements - current and future – Information outlines– Sources of data– Processes to be applied– Restrictions on data occurrences, either singly or

when associated with other data

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• Development of LOGICAL model– External Schema - User views of data– Conceptual Schema - Composite of all user views and

requirements

• Development of Entity Relationship Diagram– Shows the ‘natural grouping’ of data– Shows the relationships between the ‘natural groups’– Shows the modality and cardinality (1:M, optional,

mandatory, number of sets which are related)

Sem 1 2002 10 / 11


Designing a database (cont’d)

– User Rules for existence and operations on data– Dependencies of data– Life of data– Value or worth of data

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Determining what ‘data sets’ exist (entities)

Determining the relationships between these sets– Optional– Mandatory– 1 to 1 (1:1) , 1 to Many (1:M)

or Many to Many (M:N)– Unary, binary or ternary relationships– Special conditions for existence of data

Sem 1 2002 10 / 13


Expanding the Entities to Attributes

– Conditions of existence for attributes– Dependencies of attributes on a determinant– Primary Key (and its characteristics)

Primary - Foreign Key occurrences (and referred to the Entity Relationships)

Performance of the relationships on Insert, Update, Modification of the Primary and Foreign keys

Sem 1 2002 10 / 14


What are the attributes of each set ?

Data Structure Diagram

Primary Key(s), Foreign key(s)

Nullable, non nullable attributes

Suspicion of the effect of update, insert, delete operations

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Normalisation - dependencies of attributes on the Primary Key

Special conditions which could restrict some data occurrences

Self checking features ?

Long term storage requirements

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Access considerations - File Organisation and Access Methods

Indexing - Changing Structure - Secondary Indexing

Performance Requirements

Logical Path Access evaluation - Data Base and Equipment Loading

Growth, Volatility of Database - Scalability Aspects

Sem 1 2002 10 / 17


Transaction Processing - Transaction Manager, Scheduler, Recovery Manager

Stages of access to the physical database

Effect of power, software and hardware interruptions

Checkpoint, Logging facilities

Restart / Recovery / Backup outline

Sem 1 2002 10 / 18


Concurrency Aspects - multi user (transaction) control

Time stamping, Locks

Adverse effects of no or poor concurrency (optimistic and pessimistic)

Integrity Considerations - Entity, Referential, Domain,

Security of - hardware, communications, data

access limitations, authorisations

Sem 1 2002 10 / 19


Use of Data Dictionary information about data

Optimisation - query execution plan

Data Base Administration

Distributed database

Data Warehousing

Data Mining

Features of a database management system

Sem 1 2002 10 / 20


SQL - what is it ? What is its purpose ?

The commands : Create (object), delete, drop,

insert, update,

Querying with SQL– Select (list of attributes)– From (named tables)– Where (conditions for selection, including nested queries)– Group By (selection of aggregations– Having (condition for Grouping)– Order by (viewing sequence)

Sem 1 2002 10 / 21


Operators :

> < = !=

in, between

exists, not exists

any, not any

AND OR NOT

Avg, max, min, std, sum - set functions

Correlation - multiple table query

Sem 1 2002 10 / 22

An Introduction to SQL - Some TermsAn Introduction to SQL - Some Terms

In the next few overheads, there will be some terms and explanations which should help you to make the transition from the methods of data storage and file processing to that of the relational database style of storage and processing of data.

Sem 1 2002 10 / 23

More on TablesMore on Tables

Attributes which make up a row in a table are always scalar or atomic data types

They are complete in themselves and cannot be broken into smaller parts

Attributes can have constraints placed on them when– the table is created– or when the table is altered

These constraints are part of the database

Unlike spreadsheet cells, an attribute set of values can only hold data.

Sem 1 2002 10 / 24

Schemas and TablesSchemas and Tables

A Schema : is the data, the operators and the rules of the defined database

Tables can be permanent (base tables) or virtual (views)

Any operation in SQL will return a result table

Sem 1 2002 10 / 25

More TermsMore Terms

Are you ready for a few more terms ?

Try these :

Scalar Values : This is a value which is not an array - one dimension. 1 is a scalar value, 1,4 is not -it’s an array.

Literals : This is a constant which is referred to by its value. Literal 3 is ‘the integer data type having the value 3’

Column Expression : This is a calculation which will return a value for any data item in that attribute - also known as a ‘derived value’.

Sem 1 2002 10 / 26

A TransactionA Transaction

A transaction is a sequence of SQL statements which Oracle treats as a single unit

The set of changes is made permanent with the Commit statement

Part or all of a transaction can be undone with the Rollback statement

A transaction starts with the execution of the first SQL statement in the transaction and ends with either the Commit or Rollback statement

Sem 1 2002 10 / 27

A TransactionA Transaction

Oracle guarantees that a transaction has statement-level read consistency (the data stays the same while Oracle is gathering and returning it)

If a transaction has multiple queries, then each query is consistent, but not with each other

Transaction-level read consistency can be achieved with the Set Transaction Read Only - (queries only)

Sem 1 2002 10 / 28

Some GuidelinesSome Guidelines

1. The name allocated to a table, known as the table name, must be unique in the schema.

2. The attribute names used in a table must be unique in that table

3. It is good practice NOT to have a table name repeated as an attribute name in the same table (e.g. a table named Personnel could have an attribute ‘employee’ - not an attribute named ‘personnel’.)

4. It is good practice to use the same name for an attribute which occurs in other tables.

5. It is good practice to have related attributes in natural order - e.g. Person’s name, title, address, salary rather than address, person’s name, title, salary.

Sem 1 2002 10 / 29

Some Thoughts about KeysSome Thoughts about Keys

A KEY is an attribute (or a set of attributes) in a table which uniquely identifies each row in that table

There are several types of keys :

1. A candidate key - this is one of the ‘possible’ keys in a table. A an example, a motor car has a Registered Number, and also a Vehicle identification Number (VIN).

2. A surrogate key is a key with no meaning in itself. They are normally generated by the database system using some form of number generator. Users rarely see these values - except in Microsoft Access

Sem 1 2002 10 / 30

Some Thoughts about KeysSome Thoughts about Keys

Intelligent Keys : have a meaning. Longitude and Latitude of an object (say a building) uniquely identifies a building and also nominates where it is.

Super Key : This is normally a key with too many attributes in it. Some of the columns could be removed and a key would still exist. A good example is a key which contains ‘old value/new value’ such as ‘old telephone number/new telephone number’ when numbers are upgrades or altered.

A Primary Key : The unique, not null expression of the access to each row in a database table - normally constrained by a domain set.

Sem 1 2002 10 / 31

Embedded SQLEmbedded SQL

In commercial processing, SQL normally is between the database and a host programming language, passing data in either a forward or backward direction ( accepting new data, or returning results of queries.)

The host program communicates with the ‘outside world’

There are also PC tools which are designed to use SQL - PowerBuilder, Designer2000, Developer2000, Delphi are examples.

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There are 3 problems

1. SQL has a rich or extended set of datatypes which might not match those of the host program

2. The ‘Null’ may not exist in the host program language

3. SQL uses a set model of data - not a file model.

A file is processed (read, updated, deleted) one record at a time

A set in SQL is read, updated, deleted ‘all at once’

Embedded SQL handles these problems.

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• Embedded SQL provides for SQL statements to be recognised by the keywords ‘exec sql’ preceding the SQL commands.

• A precompiler converts the SQL statements into host language procedure calls.

• The database calls are part of an Application Program Interface library

Sem 1 2002 10 / 34

New SQL Commands and FeaturesNew SQL Commands and Features

The OLAP functions proposed for SQL-99 are

ceiling percentile_cont regr_slope

corr percent_rabk regr_sxx

covar_pop power regr_sxy

covar_samp range regr_syy

cume_dist rank row_number

dense_rank regr_avg sqrt

exp regr-avgx stddev_pop

floor regr_agvy stddev_samp

ln regr_count car_pop

moving_avg regr_intercept var_samp

moving_sum regr_r2

Sem 1 2002 10 / 35

New SQL Commands and FeaturesNew SQL Commands and Features

The principal statistical functions are ;

correlation covariance

cumulative distribution ranking

percentile linear regression

standard deviation variance

Sem 1 2002 10 / 36

Business IntelligenceBusiness Intelligence

Analysis is a fundamental to Business Intelligence

For example :-

Is there a correlation between the frequency of Web site visits (hits) and customer profitability

Who would be the ‘interested parties’ to the results of this analysis ?

Sem 1 2002 10 / 37


Some other features:

Not all DBMS’s offer the same facilities

Not all SQL software supplier versions are the same

Some interesting differences : data types, (money, currency, number - with or without ‘decimal’ provision)

Nulls and their processing capabilities

Aggregate functions especially in the handling of nulls

Sem 1 2002 10 / 38

Some Commands You Have MetSome Commands You Have Met

• Create : table, view, index, sequence (also create as select ..)

• Drop : table, view, index, sequence

• Insert : Adds a single row to an existing table

• Delete : Deletes a row or rows or all contents from an

existing table• Update : Updates a row or rows

• SqlLoad : Loads bulk data from an external file to the current database table (sqlldr80 for Personal Oracle)

Sem 1 2002 10 / 39

Some Commands You Have MetSome Commands You Have Met

• Alter : With care, provides alteration to some of the table attributes and properties

• Copy : Copies data from 1 database to a named database

• Export : Copies data from a named table in a database to the Operating system level

• Import : Copies data from the Operating system level to a named database

• Union : Combines 2 tables into 1

Sem 1 2002 10 / 40

The Query FormThe Query Form

• The form of a Query :

Select (list of attributes)

From (table, or list of table names)

Where (conditions of selection)

Group By (used for aggregate functions)

Having (conditions of selection of the Group By)

Order By (determines the order of content displayed from the Result table - Ascend, Descend on a

named attribute)

Sem 1 2002 10 / 41

Operators and PredicatesOperators and Predicates

• Arithmetic : + - / * **

• Logical : And Or Not

• Comparison Predicates : = > < <= >= <> != ^=

• Like Predicate : Pattern matching or Not matching

• Between Predicate : Numeric valued constraints

• In Predicate : String or numeric lists

Sem 1 2002 10 / 42

More PredicatesMore Predicates

• Any

• All

• Exists

Sem 1 2002 10 / 43

ConstraintsConstraints

• Null (and Not null)

• Unique

• Check (attribute property limit - In, Between )

Aggregate Functions

Count, Sum, Average, Minimum, Maximum

and don’t forget the ‘additional’ functions in SQL99

Sem 1 2002 10 / 44

Data TypesData Types

• Varchar2(number) e.g. varchar2(15)

• Number(p,s) e.g. number (10,2) 8 whole number values, 2 decimal values)

• Date

• Blob - Binary large object

• Clob - Compressed binary large object

• Other datatype supported by Microsoft - currency, long and short integer, text, various temporal options

Sem 1 2002 10 / 45

The Exam PaperThe Exam PaperThe Exam PaperThe Exam Paper

A few words about the exam :

The paper consists of 2 parts

You should read the paper completely before you attempt to answer anything

Use the text and the overheads and notes which you received during the course

Sem 1 2002 10 / 46

The ExaminationThe ExaminationThe ExaminationThe Examination

In answering questions, use• diagrams• text• note• point form - whichever you feel best suits• examples

(Not Part A)

Sem 1 2002 10 / 47


Exam in Part A 20 multiple choice questions (40)

Part B 6 short essay type questions

Answer any 3 (60)

- includes some SQL scripts

- short thesis type questions

Only answer the number of questions required.

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• Make sure your Name is on all materials handed in

• Send in via email or post or deliver all required materials

• Responses returned by Friday 21st June, 2002

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Sem 1 2002 10 / 1 Course Review We’ve made it to Lecture 10 This is the last lecture in the Course...

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