cse3180 summer 2005 lect 06 / 1 features of a dbms

CSE3180 Summer 2005 Lect 06 / 1

Features of a DBMS Features of a DBMS


Lecture 6Lecture 6

This lecture will cover many of the functions required of a Database Management System.

It is a good opportunity to review much of the material covered to date, and will also open the way to other topics such as Data Dictionary, Integrity, Recovery, Concurrency considerations and Business Rules.

We will be moving from the Logical Design, through the Implementation Planning stage to the Physical Design stage of database design.


A Slight InterludeA Slight Interlude

• Before we do, here is an answer to the puzzle which kept you awake last night.

Source Target Time Progressive

C and D move across(A,B) C,D 2 2

D returns (A,B,D) C 1 3

A and B move across (D) A,B,C 10 13

C returns (C,D) A,B 2 15

C and D move across A,B,C,D 2 17


DBMS OutlineDBMS Outline

Multi Server Multi Server Multi Server Dbms Dbms Dbms

Multi-Server Logging and Locking System

Data Base


DBMS Block DiagramDBMS Block Diagram

General Communications

GCF

Sequencer / DispatcherSCF

Parser Optimiser QueryExecution

PSF OPF QEF

Relation Query Abstract Description Storage

RDF QSF ADF

Data Manipulation DMF

Compatibility

Library

Data Type


DBMS ComponentsDBMS Components

3. Parser Facility

Parses query text and builds query tree

Stores query tree in QSF (Query Storage)

Notifies SCF (Sequence/Dispatch) that control must now pass to OPF (Optimiser)

4. Optimiser Facility

Reads query tree in QSF

Builds optimal query plan and stores plan in QSF



7. Query Storage - Support Facility

Common Storage Pool for passing objects between

(Size is user option) PSF, OPF, and QEF

Stores Query Plans

A number of stored query plans can be controlled by user



9. Data Manipulation Facility

The Access Methods - btree, hash, isam, heap, bitmap - manages internal page cache

Handles Transactions - locking - deadlocks - logging

Handles Modify and Sorting



10. Compatibility Library

- Insulates DBMS from the operating system

- Handles all I/O, string comparisons

- Associated with ' porting ' - is the component which changes and accommodates F.E's


DBMS FunctionsDBMS Functions

1. Data Storage, Retrieval and Update

2. A User-Accessible Catalogue (Dictionary)

3. Support for Shared Update

4. Backup and Recovery Services

5. Security

6. Integrity

7. Data Independence

8. Utility Services


DBMS FunctionsDBMS Functions

The Primary Objectives of a DBMS are to providefacilities for :

1. Definition of Database Logical Structures

2. Definition of Physical Structures

3. Access to the Database

4. Definition of Storage Structures to store user data

These components are known as the ‘database architecture’


Data Dictionary - Also known as the Catalog (ue)

Data Dictionary - Also known as the Catalog (ue)


Data DictionaryData Dictionary

A DATA DICTIONARY contains the fundamental definitions, characteristics and uses of data

It describes: What the data is

Characteristics

Uses of Data

User Permits / Restrictions

A DATA DIRECTORY contains information relating to Physical Data Storage



A Data Dictionary SYSTEM stores

maintains

provides access

to the Data Dictionary.

It is a set of software

Also known as the Catalog Function

The Dictionary contains information on

Data Processes Environment


A representation of a ‘database’

The System Catalogue / Dictionary

User Tables, Views, Sequences

Procedures, Indexes, User Space

Instance(s)



A Data Dictionary is a DATABASE about the data held in the USER DATABASE

Term Used : META DATA



A Data Dictionary can provide data about

1. Relationships between dictionary entity types :

item uses item ,module

table uses item, group, module

module uses item, group, file, module

program uses file, module

system uses program, system

2. Listing of all entities

Relationship reports (Which programs use record zzz)

Versioning support

Password support

User access and exits



systemplanning

Requirementsdefinitionanalysis

Design

Implementation

Testing

Operations andmaintenance

DATA

DICTIONARY

database



Data Dictionary - - - - - - - - - - - - - - - - - - - - -

HumanInterfaces

Software andDBMS Interfaces

Compilers Application Integrity PreCompilers Programs/ Constraints Report Generators

Database Application EndAdministration Programmers Users



Some Benefits from Data Dictionary Use:

1. Better data management - Redundancies, Standards, Documentation

2. Reduction in system development time - Cross reference listings, Auto copy libraries

3. Reduction in maintenance costs

4. Quicker and More Accurate changes possible

5. Documentation standards

6. Data Audit - cross references, 'where used' listings


Some of the 770 DBA TablesSome of the 770 DBA Tables

DBA_VIEWS USER_CLU_COLUMNS

ALL_ERRORS USER_AUDIT_STATEMENT

ALL_TABLES USER_AUDIT_TRAIL

ALL_OBJECTS USER_CATALOG

USER_COLL_TYPES USER_TAB_PRIVS

USER_COL_COMMENTS USER_ARGUMENTS

USER_COL_PRIVS USER_ALL_TABLES

USER_COL_PRIVS_MADE USER_TAB_PRIVS

USER_ASSOCIATIONS V$SQL

USER_AUDIT_OBJECT V$SQLAREA

USER_AUDIT_SESSION V$SHARED_MEMORY

USER_VIEWS GV$DISPATCHER


IntegrityIntegrity


IntegrityIntegrity

Integrity is a collection of processes, procedures and techniques which are used to ensure that data held in a database is

COMPLETE

ACCURATE

CLEAR

thus ensuring that Information derived from the database also has these characteristics


IntegrityIntegrity

C.R.U.D.E.

C Column Integrity - Linked to Domain Integrity

R Referential Integrity

U User Defined Integrity

D Domain Integrity - A user defined datatype

E Entity Integrity


Database IntegrityDatabase Integrity

Some terms you will encounter:

Entity Integrity

Referential Integrity

Functional Dependency (constraints between determinants

and attributes. For each value of the determinant there is only one value for each of the attributes it determines)

Multivalued Dependency

Join Dependency

Domain Constraints

Cardinality Constraint

User Defined Constraints


Data IntegrityData Integrity

General Principle: Data compliance with a set of rules

Rules Location: Best embodied in the DBMS

If they are contained in an application, there is the danger of saturating a network and causing degraded performance.

This is particularly so in client / server computing

CONSTRAINTS: Declarative approach where integrity constraints are ‘declared’ as part of a table specification. ANSI SQL-99 standards include specifications for integrity constrains syntax and behaviour


INTEGRITY CONSTRAINTSINTEGRITY CONSTRAINTS

DATABASE INTEGRITY

Refers to correctness and consistency of data

Quality Assurance

Usually expressed in terms of CONSTRAINTS

- consistency rules which must not be subverted


Forms of ConstraintsForms of Constraints

1. ENTITY INTEGRITY - Primary Key Value

NO attribute of a primary key value may be NULL

2. REFERENTIAL INTEGRITY - Foreign Key Values

If a FOREIGN KEY exists in a relation, then either

(1) the foreign key value MUST match the Primary Key value of some row in its home (or Primary) relation OR

(2) the FOREIGN KEY must be NULL

3. FUNCTIONAL DEPENDENCY - Determinant

For each value of the DETERMINANT, there must be only ONE value for each of the attributes which it determines



4. MULTIVALUED DEPENDENCIES

If A,B and C are three sets of attributes, then A

multidetermines B if and only if the set of B values

associated with each A value is independent of the C values

5. JOIN DEPENDENCY - Relation Reconstruction

A relation can be reconstructed by taking the join of its projections

6. DOMAIN CONSTRAINT - Value restrictions

Possible values of a data item are restricted to a specific set called the DOMAIN



7. CARDINALITY CONSTRAINT

The number of entities which can be related is subject to a constraint

8. SET RETENTION CONSTRAINT

The deletion of records is subject to limitations

9. EXISTENCE DEPENDENCY

Hierarchical model (also OODB). Dependency of a child on the parents limits insertion and deletion of segments



10. GENERAL CONSTRAINTS

Those restrictions which can be expressed as arbitrary predicates about the data.

e.g. no class may be scheduled for Room B.215 after 2.00pm on Fridays

General Comments: DBMS’ have deficiencies in their ability to express and enforce constraints.

Oracle uses ‘Triggers and Constraints’ and later versions of SQL use a mechanism called ASSERTIONS.


Referential IntegrityReferential Integrity

Foreign Key Concept - An attribute (or set of attributes)in one table (the referencing table) occurs as the Primary Key of another table (the Primary, Lookup or Referenced table)

Referential Integrity Constraint:

The Value of a Foreign Key Must Be a Key Value

in the Referenced Table

OR

The Value of the Foreign Key Must Be Undefined (Null)

This cannot occur if the Foreign Key is part of the Primary Key of the Referencing Table


Possible Referential Integrity ProcessesPossible Referential Integrity Processes

1. Limited Insert : If an incoming Foreign Key DOES NOT EXIST as a referenced table Primary Key:

ABORT TRANSACTION - REPORT

2. Limited Update : If an incoming Foreign Key DOES NOT EXIST as a referenced table Primary Key

TERMINATE PROCESS

3. Restricted Delete : If there are referencing FOREIGN KEYS in a referencing table

TERMINATE DELETE PROCESS ON REFERENCED TABLE



4. Restricted Update : If there are referencing Foreign Keys in a referencing table

INHIBIT UPDATE OPERATION ON THE REFERENCED KEY

5. Cascade Delete : If there are Referenced Keys

INITIATE DELETION OPERATION ON REFERENCED TABLE BY DELETING ALL REFERENCING ROWS

6. Cascade Update : Commence an UPDATE on the REFERENCED TABLE by UPDATING the Foreign Keys

on all Referencing Rows in the Referencing Table(s)



7. Nullify Delete : Commence a DELETE operation on the REFERENCED table by setting ALL the FOREIGN

KEYS on the Referencing Table(s) to NULL (watch Data Types)

8. Nullify Update : Set all of the Foreign Keys of the Referencing Table to NULL. This will invalidate any

referencing of the Referenced Key (which must not be NULL)

9. Default Update : Invalidate references to Updated Referenced Keys by setting all Referencing Table

Foreign Keys to a DEFAULT value



10. Default Delete : Invalidate references to the deleted Referencing Key Value(s) by setting all Referencing Foreign Key values to a DEFAULT value

11. Warning Delete : Permit the deletion BUT Warn the user of the Unattached Foreign Keys which are now present in the Referencing Table(s)

12. Warning Update : Permit the Update BUT Warn the User of Unattached Foreign Keys which are now present in the Referencing Table(s)


A Deeper Look into a DBMS


CLOSURE (Relational Algebra)CLOSURE (Relational Algebra)

Inference Rules; Armstrong’s Axioms

(Rules for Inference for Functional Dependencies)

Premise:

If F is a set of functional dependencies of relation R, the set of ALL FUNCTIONAL DEPENDENCIES which can be derived from F, called F+, is called the closure of F



1. REFLEXITIVITY : If B is a subset of A, then A ----> B

2. AUGMENTATION : If A ---> B, then AC ---> BC

3. TRANSITIVITY : If A ---> B, and B ---> C, then A ---> C

4. ADDITIVITY or UNION

If A --->BC, then A---> C and A ---> B



5. PROJECTIVITY or DECOMPOSITION

If A ---> BC, then A--->C and A ---> B

6. PSEUDOTRANSITIVITY

If A --->B, and CB --->D, then AC ---> D



The RESULT of a query is another table,

and therefore the output from operation can become the input to another operation

It is possible to to take:

(a) a projection of a union

(b) a join of 2 (or more) restrictions

(c) the difference of a join and a restriction

And it is possible to express nested relational expressions

- the operands are represented by expressions


Relational AlgebraRelational Algebra

8 Basic Operators

Traditional Set Operators Special Relational Operators

Union Select

Intersect Project

Difference Join

Cartesian product Divide

High level operators act on ONE or MORE relations producing a NEW relation as a result ------> CLOSURE

Most relational DBMS will support SELECT, PROJECT and JOIN


UNIONUNION

The UNION of 2 union compatible relations A and B is the set of all rows belonging to either A or B or both

employee salespersonempid name born empid name born10314 Smith 10-03-1961 10911 Jones 16-08-197210862 Black 23-05-1946 10314 Smith 10-03-1961

employee union salespersonempid name born10314 Smith 10-03-196110862 Black 23-05-194610911 Jones 16-08-1972 Notice the elimination of

duplicate records


Difference Special OperatorDifference Special Operator

The DIFFERENCE between 2 UNION COMPATIBLE relations, A minus B, is the set of all rows belonging to A and NOT to B.

See previous for the relations A and B

RESULT: EMPLOYEE DIFFERENCE SALESPERSON

empid name born

E7 BLACK 23-05-1946


Intersection OperatorIntersection Operator

The intersection of 2 UNION COMPATIBLE relations is the set of all rows which belong to A and B.

EMPLOYEE INTERSECTION SALESPERSON

empid name born

E1 SMITH 10-03-1961


CARTESIAN PRODUCTCARTESIAN PRODUCT

The Cartesian Product of 2 relations, A times B, is every possible combination of rows from each relation

PART SUPPLIER

partid partname supplierid suppliername

P1 NUT S1 SMITH

P2 BOLT S2 JONES

P3 WASHER

partid partname supplierid suppliername

P1 NUT S1 SMITH

P2 BOLT S1 SMITH

P3 WASHER S1 SMITH

P1 NUT S2 JONES

P2 BOLT S2 JONES

P3 WASHER S2 JONES


Special SELECT OperatorSpecial SELECT Operator

Creates a 'Horizontal subset' of a relation by satisfying a condition

EMPLOYEE

empid name deptid projectid

E1 GOLD D1 P1

E2 BLUE D6 P1

E3 WHITE D1 P2

E4 RED D1 P3

E5 BROWN D6 P3

select employee where projectid = p1 or projectid = p2

RESULT empid name deptid projectid

E1 GOLD D1 P1

E2 BLUE D6 P1

E3 WHITE D1 P2


PROJECT Special OperatorPROJECT Special Operator

Creates a 'vertical subset' of a relation by projecting only certain attributes of a relation. Duplicate rows are removed.

See previous. Project Employee over projectid giving Result2

RESULT2

projectid

P1

P2

P3


JOIN Special OperatorJOIN Special Operator

Combines 2 or more relations (tables) based on specified conditions between attributes in each table. (The attributes must have the same domain to be meaningful)

SKILL SKILL_EMP

skillid name empid skillid

S1 database E1 S1 Equi-Join The Join condition is =

S2 C++ E1 S4

S3 Ingres E3 S3 Natural Join One of the two

S4 Analysis E5 S2 identical attributes in an equijoin

E5 S4

Join skill_emp and skill where skill.skillid = skill_emp.skillid giving result3 Result3

empid skillid skillid(skill) name

E1 S1 S1 database Any others ?


Joining a Table to ItselfJoining a Table to Itself

Typical Query: For each employee, list the employee number, name Manager and Manager’s name

Select X.EMPID, X.NAME, X.MGR, Y.NAMEfrom EMP X, EMP Y (same table contents - ‘mirrored’)where X.MGR = Y.EMPID

Result: EMPID NAME MGR NAME 10 SMITH 40 BROWN 20 JONES 40 BROWN 30 BLACK 40 BROWN 40 BROWN 50 WHITE

The Primary Key and the Foreign are both in the same table

Two virtual tables are created for joining (‘alias’ feature)


Outer JoinOuter Join

EMP DEP

EmpId Name Age DepId Mgr DepId Name Loc

10 smith 25 15 40 11 MIS Caulfield

20 jones 28 15 40 20 Finance Malvern

30 black 20 40 15 Market City

40 brown 46 11 50 17 Accounts Clayton

50 white 42 11

Select d.depid, e.name, e.age The + appends a null row to the EMP table

From dep d , emp e for this query and it is used to join to the

where d.depid = e.depno (+) DEP rows with no matching employee details

DepId name age DepId name age

11 brown 46 15 jones 28

11 white 42 20 black

15 smith 25 17


The joining of attributes depends on certain types of relationships;

Consider two attributes C1 and C2 which are join attributes

There are 4 types of relationships possible

• (a) the values of C1 and C2 are equal• (b) the values of C1 are a subset of those of C2 (or vice

versa)• (c) the values of C1 and C2 are conjoint - they have some

values in common• (d) the values of C1 and C2 are disjoint - they have no

values in common

Joins of Tables


Joins of Tables

In set theory, these take the forms

(a) C1 = C2

(b) C1 C2 or C2 C1

(c) C1 - C2 0 or C2 - C1 0(d) C1 - C2 = C1 and C2 - C1 = C2


There are a number of possible ‘join’ types allowable in the relational model

They are:

• 1. Thetajoin 2.Equijoin• 3. Natural join 4. Inner join• 5. Outer join 6. Left Outer join• 7. Right Outer join 8. Full Outer join

Joins of Tables


DIVISIONDIVISION

• Divides a BINARY relation by a UNARY relation and produces a UNARY relation as a result.

empid skillcode skillcode empid

E1E2E3E2E5E6

S1S2S3S4S5S6

S2S4

E2

Divide emp-skill by skill-reqdto give result

emp-skill skill-reqd result

Special note: JOIN, INTERSECTION and DIVISION can be defined in terms of the other 5 operators (which are known as the ‘primitive’ operators).


A DIVISION exampleA DIVISION example

In the Air Transport Industry, pilots records contain details of the aircraft they are qualified to fly. And there are also records of the number and types of aircraft in the hangers and which Company owns what.

In this case, the table of pilot’s names and the planes they can fly is the dividend

The details of the planes in the hangars is the quotient

The query is to obtain the names of the pilots who can fly every type of plane in the hangars


Suggested SolutionSuggested Solution

• create table pilotskill (pilot vchar (150) not null,

plane vchar(15) not null);• create table hangar (plane vchar(15));

• select pilot from pilotskill ps1, hangar h1

where ps1.plane = h1.plane

group by ps1.pilot

having count(ps1.plane = select count(*) from hangar);

[notice the absence of any ‘division’ operator - this is effectively performed by the execution plan]


Division ExamplesDivision Examples

A B 1 J 1 K 1 L 2 J 2 K 3 K 3 L 3 J

C J K L

1 3

Result


Division ExamplesDivision Examples

Name Degree

Jones B ScJensen B ScJensen M ScJensen PhDSmith B ScSmith M ScRogers B ScRogers PhD

M ScB ScPhD

D1 D2B ScM Sc

D3B Sc

R1Jensen

R2JensenSmith

R3 Jones Jensen Smith Rogers


Relational Algebra Operators Relational Algebra Operators

Select Project

abc

xy

a xa yb xb yc xc y

Cartesian Product

Union IntersectionDifference


Relational Algebra OperatorsRelational Algebra Operators

a1 b1 a2 b1 a3 b2

b1 c1 b2 c2 b3 c3

a1 b1 c1 a2 b1 c1 a3 b2 c2

Natural Join

a x a y a z b x c y

xy

a

Divide


Data Base DesignData Base Design4th Generation Environment - User Perception

user terminal

teleprocessing report query electronicmonitor writer language mail

applicationprograms

data dictionaryDBMS

database

structured and non-structured dataimages, graphics, video,voice

e-mailfiles


DBMS Command LevelsDBMS Command Levels

DataBase Administrators Priviliged set of commands. Sometimes called 'superuser'

Data Administration

Database Developers

Application Developers

Users with Query rights only

Users with Table modification rights

cse3180 summer 2005 lect 06 / 1 features of a dbms

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