review summary for cs490

8/7/2019 Review Summary for CS490

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CS490 Database Management System

Section 1 2 3 4 5 6 7

What do you need in Application Development?

Feasibility

Analysis

Design

Development

Implementation

Mention four steps for database design:

Identify business rules.

Define tables and relationships.

Create input forms and reports.

Combine as applications for users.

Mention the components of a DBMS?

Database engine

The heart of the DBMS. It responsible for storing, retrieving, and

updating the data.

Data dictionary

Holds the definitions of all of the data tables.

Query ProcessorIt enables developers and users to store and retrieve data.

Report writer

Enables you to set up the report on the screen to specify how items will

be displayed or calculated.

Forms generator (input screens)

Helps the developer create input forms (enter data).

Application generator

A collection of forms and reports designed for a specific user task.

A good DBMS contains an application generator.

Prepared by: Dr. Saatchi, Seyed Mohsen 3/44


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Section 1 2 3 4 5 6 7

Communications

Security & other Utilities

Mention the Advantages of Database Approach:

Minimal data redundancy.

Data consistency.

Integration of data.

Sharing of data.

Enforcement of standards.

Ease of application development.

Uniform security, privacy and integrity.

Data independence.

Database Management Approach

Data is most important

Data defined first

Standard format

Access through DBMS

Queries, Reports, Forms

Application Programs

3GL Interface Data independence

Change data definition without changing code

Alter code without changing data

Move/split data without changing code

Mention some drawback problems

Uncontrolled Duplication

Inconsistent data

Inflexibility Limited data sharing

Poor enforcement of standards

Poor programmer productivity

Excessive program maintenance


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Section 1 2 3 4 5 6 7

Mention some of Database Types:

Hierarchical Database: To retrieve data, you must start at the top &

retrieve all nested data

Network Database

Relational Database

Object-Oriented DBMS

__________________A DBMS tool that assists the developer in creating a

complete application package. Common tools include menu and toolbar

generators and an integrated context-sensitive Help system.

Application generator

__________________ A collection of data stored in a standardized format,designed to be shared by multiple users. A collection of tables for a

particular business situation.

Database

__________________ the heart of the DBMS. It is responsible for storing,

retrieving, and updating the data.

Database Engine

_________________Software that defines a database, stores the data,supports a query language, produces reports, and creates data entry screens.

Database Management System (DBMS)

___________________holds the definitions of all of the data tables and

describes the type of data that is being stored.

Data Dictionary

___________________ separates the data from the programs, which often

enables the data definition to be changed without altering the program.

Data independence



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Section 1 2 3 4 5 6 7

___________________ a quick examination of the problems, goals, and

expected costs of a proposed system. The objective is to determine whether

the problem can reasonably be solved with a computer system.

Feasibility study

___________________ A DBMS tool that enables you to set up input forms

on the screen.

Forms Generator

___________________An older DBMS type that organizes data in

hierarchies that can be rapidly searched from top to bottom, e.g., Customer

OrderOrder Item.

Hierarchical Database

_________________An older DBMS type that expanded the hierarchical

database by supporting multiple connections between entities. A network

database is characterized by the requirement that all connections had to be

supported by an index.

Network Database

__________________A database system that holds objects, including

properties and methods. It supports links between objects, including

inheritance.Object-oriented (OO) database

__________________The use of a database for data analysis. The focus is

on retrieval of the data. The primary goals are to provide acceptable

response times, maintain security, and make it easy for users to find the data

they need.

Online Analytical Processing (OLAP)


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Section 1 2 3 4 5 6 7

____________________In object-oriented programming, the ability to store

objects (in a file or database) so that they can be retrieved at a later

Data.

Persistent Objects

_________________In SQL-99 a proposed method for storing methods

associated with objects. The module code would be stored and retrieved

automatically by the DBMS.

Persistent stored modules

__________________The most popular type of DBMS. All data is stored in

tables (sometimes called relations). Tables are logically connected by the

data they hold (e.g., through the key values). Relational databases should bedesigned through data normalization.

Relational Database

_________________A DBMS tool that enables you to set up reports on the

screen to specify how items will be displayed or calculated. Most of these

tasks are performed by dragging data onto the screen.

Report writer

_________________I inherits all of the columns from a base table. It

provides inheritance similar to that of the abstract data types; however, all

data is stored in separate columns.

Sub Title



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Section 1 2 3 4 5 6 7

Section 2: Data Design

Organizations are particularly interested in evaluating benefits in three key

areas:

Reduction of costs.

Increase in sales or revenue.

Competitive advantage.

Three common types of models used to design system:

Process models.

Class or object models. Event models.

Initial steps in database design:

Identify the exact goals of the system.

Talk with the users to identify the basic forms and reports.

Identify the data items to be stored.

Design the classes (tables) and relationships.

Identify any business constraints.

Verify the design matches the business rules.

For the initial design you need three basic pieces of information:

The data that needs to be collected.

The data type.

The amount of data involved.

What is an Entity?

Some item in the real world that you wish to track.

Entity i.e. described by attributes or properties.

What is a Class?

Entity listed with its properties.


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Section 1 2 3 4 5 6 7

What is a Method?

A function that is performed by the class.

What is a Class diagram?

Displays each class as box containing the list of properties for the class.

Association:

A relationship between two or more classes.

Relational database:

A collection of tables.

Table:A collection of columns (attributes) describing an entity.

Two important aspects to a relational database are:

1- All data must be stored in tables.

2- All tables must be carefully defined tp provide flexiplity and minimize

problems.

Data normalization:

The process of defining tables properly to provide flexibility, minimizes

redundancy, and ensure data integrity.

Note: The aim of Data normalization is to produce a list of nicely behaved tables.

Primary Key:

Is a column or set of columns that identifies a particular row?

Note: In most cases separate keys will be created to ensure they are unique.

Note: The relationship between the primary key and the rest of the data is

one to one.

State there types of relationships:

One-to-One

One-to-many

Many-to-many



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Section 1 2 3 4 5 6 7

Sample Association Rules (Multiplicity)

There is a problem with relation many to many, how can we solve it?

By make all many to many relationships be converted to a set of one to

many relationships by adding new entity.

Association Details: Aggregation

The Sale consists of a set of Items being sold.

Note: If order did matter, you would simply put the notation (ordered)

underneath the association.

Association Details: Composition

Is a stronger aggregate association that does arise more often?Aggregation where the components become the new object.

Association Details: Generalization

What meant by Inheritance?

Means that the object in the derived classes have all of the properties

from the higher classes, as well as those defined in their own class.

Class hierarchy:

Which shows how classes are derived from each other, and highlights whichproperties and functions are inherited?

What meant by Reflexive association:

A relationship from one class back to itself.

Data type:

Text Numbers Dates & Times

Event Examples

Business Even Data Event

User Event


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Section 1 2 3 4 5 6 7

Design Importance: Large Projects

Design is harder on large projects.

Communication with multiple users.Communication between IT workers.

Need to divide project into pieces for teams.

Finding data/components.

Staff turnover--retraining.

Need to monitor design process.

Evaluation.

Build systems that can be modified later.

Documentation.

Communication/underlying assumptions and model.

AggregationThe generic name for several SQL functions that operate across the selected rows. Commonexamples include SUM, COUNT, and AVERAGE.

AssociationConnections between classes or entities.

Association roleIn UML, the point where an association attaches to a class. It can be named, and generallyshows multiplicity, aggregation, or composition.

Binary large object(BLOB) A data domain for undefined, large chunks of data. A BLOB (or simple object) type canhold any type of data, but the programmer is often responsible for displaying, manipulating,and searching the data.

Class diagramA graph of classes connected through relationships. It is designed to show the static structureof the model. Similar to the entity relationship diagram.

Class hierarchy

A graph that highlights the inheritance relationships between classes.

Collaboration diagramA UML diagram to display interactions among objects. It does not show time as a separatedimension. It is used to model processes.

Section 1 2 3 4 5 6 7



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Data normalizationThe process of creating a well-behaved set of tables to efficiently store data, minimizeredundancy, and ensure data integrity. See first, second, and third normal form.

Data typeA type of data that can be held by a column. Each DBMS has predefined system domains

(integer, float, string, etc.). Some systems support user-defined domains that are namedcombinations of other data types.

Derived classA class that is created as an extension of another class. The programmer need only define thenew attributes and methods. All others are inherited from the higher level classes. Seeinheritance.Encapsulation

In object-oriented programming, the technique of defining attributes and methods within acommon class. For example, all features and capabilities of an Employee class would belocated together. Other code objects can use the properties and methods but only byreferencing the Employee object.

Composition associationA relationship in which an object is composed of a collection of other objects. For example, abicycle is built from components. In UML, it is indicated with a small filled diamond on theassociation end.


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Section 1 2 3 4 5 6 7

Section 3: Data Normalization

By designing database tables carefully it will:

Save space.

Minimize duplication.

Protect the data to ensure its consistency.

Provide faster transactions by sending less data.

Type of keys:

Primary key:

Every table (object) must have a primary key.

Uniquely identifies a row (One-to-One).

Composite keys:

Tables that will use more than one column as part of the

primary key.

We need it when the table contains a one-to-one or many-to-

many relationship with another table.

Foreign key:

It is a primary key but in other table. Customer ID is a primary key within the customer table. It is

known as a foreign key.

Surrogate keys:

Are often hidden.

What happens if two users attempt to generate a new key at the same time?

A good DBMS handles these problems automatically.

In Microsoft Access they use the auto number data type. But if

there is a new value to generate the process is not automatic.

In SQL Server: Identity data type.

In Oracle: SEQUENCES command (but require additional

programming)

Note:

A detailed class diagram can describe each table and include all properties.



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Section 1 2 3 4 5 6 7

Drawback:

Numbers are not related to any business data, so the application needs to

hide them and provide other look up mechanisms.

Note: There are problems with repeating data known as an insertion anomaly

and a deletion anomaly. These problems arise because you tried to add or

delete all the data in one table.

First Normal Form

When a table has no repeating groups, it is said to be in first normal form.

Remove repeating sections

Split into two tables Bring key from main and repeating section

There is a problem with the first normal form, which is:

Replication

Hidden dependency

Second Normal Form

Each non-key column must depend on the entire key.

Dependence (definition)If given a value for the key you always know the value of the property in

question, then that property is said to depend on the key.

If you change part of a key and the questionable property does not

change, then the table is not in 2NF.

There is a problem with the second normal form

Replication

Hidden dependency and the solution here is to split table.

Third Normal FormTo be in 3NF a table must already be in 2NF, and every non-key

column must depend on nothing but the key.


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Section 1 2 3 4 5 6 7

There is a problem in this example:

RentalForm2(TransID, RentDate, CustomerID, Phone, Name, Address, City,

State, ZipCode), so there are two solutions:

make CustomerID part of the key.

Split the table (if the tablr is already in 2NF this will be the only

choice that work).

Dependence (definition)

If given a value for the key you always know the value of the

property in question, then that property is said to depend on the

key.

If you change the key and the questionable property does not

change, then the table is not in 3NF.

3NF Rules/Procedure

Split out repeating sections

Be sure to include a key from the parent section in the new piece so the two

parts can be recombined.

Verify that the keys are correct

Is each row uniquely identified by the primary key?

Are one-to-many and many-to-many relationships correct?Check many for keys columns and one for non-key columns.

Note: Make sure that each non-key column depends on the whole key and nothing

but the key.

No hidden dependencies.

To check your tables, you essentially repeat the steps in normalization:

First: Make sure that you have pulled out every repeating group.

Second: Look at each non-key column and ask your self if it dependson the whole key and nothing but the key.

Third: Verify that the tables can be reconnected.

Fourth: Ask your self if each table represents a single object.

Finally: Enter sample data for each table and make sure that you are

not entering duplicate rows.



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Section 1 2 3 4 5 6 7

Boyce-Code Normal Form (BCNF)

There are an a problem which is Hidden dependency

Fourth Normal Form

Technically, if you keyed every column, any table would be in 3NF, which

does not solve any problems.

Note: In some cases, there are hidden relationships between key properties.

Domain-Key Normal Form (DKNF)

If a table is in DKNF, Fagin proved that it must also be in 4NF, 3NF and all

of the other normal forms.

The goal of DKNF:

To have each table represent one topic and for all the business rules to

be expressed in terms of domain constraints and key relationships.

Table will always be in 4NF.

Drawbacks No mechanical method to get to DKNF

No guarantee a table can be converted to DKNF

Rules Table => one topic

All business rules explicitly written as domain constraints and key

relationships.

No hidden relationships.

Data Rules and IntegrityNote: One of the goals of a database designer is to ensure that the data remains

accurate.

Type of data integrity: Type of constraint is to choose data from a set of predefined options.

Type of data integrity is a bit more complicated but crucial in a relational

database.


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Section 1 2 3 4 5 6 7

Referential integrity

Exists when a value for a foreign key can be entered only if the

corresponding value already exists in the originating table.

Auto numberA type of data domain where the DBMS automatically assigns a unique identification numberfor each new row of data. Useful for generating primary keys.

Boyce-Code normal form(BCNF) All dependencies must be explicitly shown through keys. There cannot be a hiddendependency between non-key and key columns.

Cascading deleteWhen tables are linked by data, if you delete a row in a higher level table, matching rows inother tables are deleted automatically. For example, if you delete Customer 1173, all ordersplaced by that customer are also deleted.

Composite keyA primary key that consists of more than one column. Indicates a many-to-many relationshipbetween the columns.

Data dictionaryHolds the definitions of all of the data tables and describes the type of data that is beingstored.

Data integrityKeeping accurate data, which means few errors and means that the data reflects the truestate of the business. A DBMS enables you to specify constraints or rules that help maintainintegrity, such as prices must always be greater than 0.

Data volumeThe estimated size of the database. Computed for each table by multiplying the estimatednumber of rows times the average data length of each row.

Default valuesValues that are displayed and entered automatically. Used to save time at data entry.

Deletion anomalyProblems that arise when you delete data from a table that is not in third normal form. Forexample, if all customer data is stored with each order, when you delete an order, you couldlose all associated customer data.

DependenceAn issue in data normalization. An attribute A depends on another attribute B if the values of A

change in response to changes in B. For example, a customer's name depends on theCustomer ID (each employee has a specific name). On the other hand, a customer's namedoes not depend on the Order ID. Customers do not change their names each time they place

an order.

Domain-key normal form(DKNF) The ultimate goal in designing a database. Each table represents one topic, and all ofthe business rules are expressed in terms of domain constraints and key relationships. That is,all of the business rules are explicitly described by the table rules.

Section 1 2 3 4 5 6 7



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First normal form(1NF) A table is in 1NF when there are no repeating groups within it. Each cell can containonly one value. For example, how may items can be placed in one Order table? The itemsrepeat, so they must be split into a separate table.

Foreign key

A column in one table that is a primary key in a second table. It does not need to be a key inthe first table. For example, in an Order table, Customer ID is a foreign key because it is aprimary key in the Customer table.

Fourth normal form(4NF) There cannot be hidden dependencies between key columns. A multi valued dependencyexists when a key determines two separate but independent attributes. Split the table to makethe two dependencies explicit.

Hidden dependencyA dependency specified by business rules that is not shown in the table structure. It generallyindicates that the table needs to be normalized further and is an issue with Boyce-Code orfourth normal form.

Insertion anomalyProblems that arise when you try to insert data into a table that is not in third normal form.For example, if you find yourself repeatedly entering the same data (e.g., a customer'saddress), the table probably needs to be redefined.

Master-detailA common one-to-many relationship often found on business forms, where the main form(e.g., Order) displays data for the master component, and a sub form (e.g., Order Items)displays detail data. Sometimes called a parent-child relationship.

MetadataData about data, or the description of the data tables and columns. Usually held in the datadictionary.

Referential integrityA data integrity constraint where data can be entered into a foreign key column only if thedata value already exists in the base table. For example, clerks should not be able to enter anOrder for Customer ID 1173 if Customer ID 1173 is not in the Customer table.

Repeating groupsGroups of data that repeat, such as items being ordered by a customer, multiple phonenumbers for a client, and tasks assigned to a worker.

Second normal form(2NF) A table is in 2NF if every non key column depends on the entire key (not just part of it).This issue arises only if there is a concatenated key (with multiple columns).

Third normal form(3NF) A table is in third normal form (3NF) if each non key column depends on the whole keyand nothing but the key.


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Section 1 2 3 4 5 6 7

Section 4: Introduction to Queries

Note: Query system is becoming more standardized, so that developers and

users can learn one language and use it on a variety of different system.

What meant by SQL?

Is the standard database query language.

Note: Most database system provides a query by example (QBE) method to

help beginners create SQL queries.

Three tasks of a query language:

define the database (DDL)

Change the data.

Retrieve data.

Note: The SELECT command is used to retrieve data.

SELECT command is to retrieve specified columns of data for rows that

meet some criteria.

Four Questions to Create a Query:

What output do you want to see?

What do you already know (or what constraints are given)?

What tables are involved?

How are the tables joined together?



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Section 1 2 3 4 5 6 7

Section 5: Advanced Queries

Note: One of the most powerful features of the SQL SELECT command.

Two key points will help you learn how to use sub queries:

1- SQL was designed to work with sets of data avoid thinking in terms

of individual rows

2- You can split nested queries into their separate parts and deal with

the parts individually.

Note: Some special SQL operators (IN, ALL, ANY, EXISTS)

Sub query with ANY and ALL

The ANY and ALL operators combine comparison of numbers with

subsets.

Word SOME can be used in place of the word ANY.

OUTER JOINS

The INNER JOIN command instructs the DBMS to match every entry in the

Sel-Animal table with a corresponding Animal ID in the Animal table.

Note: The OUTER JOIN describes what should happen when values in one

table do not exist in the second table.

In joining two tables, you have to consider two basic situations:

1- A value might exist in the left table with no matching value in the

right table.

2- A value might exist in the right table with no matching value in the

left table.

Correlated Sub query are Dangerous

Correlated Sub query a type of queries known to run for several days

without finishing.


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Section 1 2 3 4 5 6 7

UNION, INTERSECT, EXCEPT

UNION: to combines rows of data.

INTERSECT: Retrieves only the rows that are in both tables.EXCEPT: Retrieves rows that exist in only one table.

Multiple JOIN Columns

Sometimes need to JOIN tables on more than one column.

Reflexive Join

Need to connect a table to itself.

Inequality JoinWhere the comparison is made with inequality operators (less than, greater

than) instead of an equals sign.

Note: Queries with Every Need EXISTS

CREATE TABLE

Defines a new table

Constraints:

Are rules that are enforced by the database system?

SQL Data Manipulation Commands

INSERT

To insert one row of data at a time.

DELETE

To remove the older data

UPDATE

To update the record on the specific table.



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Section 1 2 3 4 5 6 7

ALL

A SQL SELECT clause often used with sub queries. Used in a WHERE

clause to match all of the items in a list. For example, Price > All (. . .)

means that the row matches only if Price is greater than the largest value in

the list.

ALTER TABLE

A SQL data definition command that changes the structure of a table. To

improve performance, some systems limit the changes to adding new

columns. In these situations, to make major changes, you have to create a

new table and copy the old data.

ANYA SQL SELECT clause often used with sub queries. Used in a WHERE

clause to match at least one of the items in a list. For example, Price > ANY

(. . .) means that the row matches as long as Price is greater than at least one

item in the list.

CASE

A SQL operator supported by some systems. It examines multiple conditions

(cases) and takesthe appropriate action when it finds a match.

ConcatenateA programming operation that appends one string on the end of a second

string. For example, Last Name & "," & First Name could yield "Smith,

John".

Constraint

In SQL, a constraint is a rule that is enforced on the data. For example, there

can be primary-key and foreign-key constraints that limit the data that can be

entered into the declared columns. Other business rules can form constraints,

such as Price 0.

Correlated sub query

A sub query that must be reevaluated for each row of the main query. Can be

extremely slow. Can often be avoided by creating a temporary table and

using that in the sub query instead.


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Section 1 2 3 4 5 6 7

CREATE DOMAIN

A SQL data definition command to create a new logical grouping of tables.

With some systems it is equivalent to creating a new database. This

command is not available in Oracle or SQL Server.

CREATE TABLE

A SQL data definition command to create a new table. The command is

often generated with a program.

CREATE VIEW

A SQL command to create a new view or saved query.

Data type

A type of data that can be held by a column. Each DBMS has predefined

system domains (integer, float, string, etc.). Some systems support user-

defined domains that are named combinations of other data types.

DELETE

A SQL data manipulation command that deletes rows of data. It is always

used with a WHERE clause to specify which rows should be deleted.

DROP

A SQL data definition command that completely removes a table from thedatabase- including the definition. Use it sparingly.

Equi-join

A SQL equality JOIN condition. Rows from two tables are joined if the

columns match exactly. Equi-join is the most common JOIN condition.

Rows that have no match in the other table are not displayed.

EXCEPT

A SQL operator that examines rows from two SELECT statements. It

returns all rows from one statement except those that would be returned bythe second statement. Sometimes implemented as a SUBTRACT command.

See UNION.

EXISTS

A SQL keyword used to determine if sub queries return any rows of data.



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Section 1 2 3 4 5 6 7

FULL JOIN

A JOIN that matches all rows from both tables if they match, plus all rows

from the left table that do not match, and all rows from the right table that do

not match. Rarely used and rarely available. See LEFT JOIN and RIGHT

JOIN.

IN

A SQL WHERE clause operator typically used with sub queries. It returns a

match if the selected item matches one of the items in the list. For example,

WHERE Item ID IN (115, 235, 536) returns a match for any of the items

specified. Typically, another SELECT statement is inserted in the

parentheses.

Inequality joinA SQL JOIN where the comparison is made with an inequality (greater than

or less than) instead of an equality operator. Useful for placing data into

categories based on ranges of data.

INSERT

Two SQL commands that insert data into a table. One version inserts a

single row at a time. The other variation copies selected data from one query

and appends it as new rows in a different table.

INTERSECT

A set operation on rows of data from two SELECT statements. Only rows

that are in both statements will be retrieved. See UNION.

LEFT JOIN

An OUTER JOIN that includes all of the rows from the "left" table, even if

there are nomatching rows in the "right" table. The missing values are

indicated by Nulls. See RIGHT JOIN and INNER JOIN. Left and right are

defined by the order the tables are listed; left is first.

OUTER JOIN

A generic term that represents a left join or a right join. It returns rows from

a table, even if there is no matching row in the other table.


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Section 1 2 3 4 5 6 7

Reflexive join

A situation that exists when a table is joined to itself through a second

column. For example, the table Employee (Employee ID. . . Manager ID)

could have a join from Manager ID to Employee ID.

Reflexive join

A situation that exists when a table is joined to itself through a second

column. For example, the table Employee (Employee ID. . . Manager ID)

could have a join from Manager ID to Employee ID.

RIGHT JOIN

An OUTER JOIN that includes all the rows from the "right" table, even if

there are no matching rows in the "left" table. The missing values areindicated by NULLS. See RIGHT JOIN and INNER JOIN. Left and right

are defined by the order the tables are listed; left is first.

Schema

A collection of tables that are grouped together for a common purpose.

Self-join

A table joined to itself. See reflexive join.

Sub query

Using a second query to retrieve additional data within the main query. For

example, to retrieve all sales where price was greater than the average, the

WHERE clause could use a sub query to compute the average price.

UNION

An SQL clause to combine rows from two SELECT statements. Both

queries must have thesame number of columns with the same domains.

Most systems also support INTERSECT and EXCEPT (or SUBTRACT)

operators.

UPDATE

A SQL data manipulation command that changes the values in specified

columns. A WHERE clause specifies which rows will be affected



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Section 1 2 3 4 5 6 7

Buttons

1. Minimize

2. Maximize

3. Close

4. Scroll box (thumb)

5. Scroll bar

Windows Menus

Drop-down

Short Cut Keys

Mnemonic character

Pop-up (as needed)

Message Boxes

1. Title

2. Message

3. Simple buttons

4. Icons

5. Modal (required)

Interface / Accessibility

1. Multiple Input Methods2. Keyboard

3. Mouse

4. Voice

5. Multiple Outputs

6. Visual

7. Sound

8. Color



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Section 1 2 3 4 5 6 7

Types of Forms

1- Tabular Single Row

Sub-forms (one-to-many)

Switchboard

2- Tabular Form

Tabular

1. Single table.

2. Designer can control data entry sequence

3. May have Buttons for sorting.

Single Row (Columnar) Form

Data for only one row

Can set optimal layout.


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Section 1 2 3 4 5 6 7

Paper forms.

Can use color, graphics, and command buttons to make the form

Easier to use

Note the importance of the navigation buttons.

Find command

Can include Sub forms

Sub-Forms

One-to-many relationship

Switchboard Form:

Blank Form

Graphics/Picture/Background

Identify User

Choose Task.

Contains copyright and usage notes



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Section 1 2 3 4 5 6 7

Menu Design

Setup Choices

Data Input

Print Reports

DOS Utilities

Backups

Form Properties

Data

Integrity (Edit, Delete)

Format (color)

Other (Pop-up menus, Help menu) Controls on Forms (Complex)

Tab

Grid

Calendar

Gauge

Slider

Spin Box

Charts

Build a query that generates the data to be graphed.

Multiple Forms

Using data on other forms


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Section 1 2 3 4 5 6 7

Subtotals and sub forms

Multi-page v Separate forms

Same record set

Screen size

Side-by-side

Integrity in Forms

Avoid relying on forms

Use forms to make it easy to enter quality data

Controls

Selectivity

User assistance

Large Projects & Forms:

Sometimes its called International Attributes

1Language

2Character sets and punctuation marks

3Sorting

4Data formats

Date- Time- Metric v English- Currency symbol and format- Separators

(decimal . . .) - Phone numbers

1Postal codes

2National ID Numbers

Creating a Graphical Approach

1Get the hardware.

2Add an object column to your table definition.

2Design the screens.1. Be creative.

2. Get user input.

3. Make the users job easier.

4. Avoid using graphics just for show.

5. Double-click

6. Drag-and-drop

7. Programming



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Section 1 2 3 4 5 6 7

Report Why?

To collect data

Summarize data

Report strength

Easily handled

Combine both detailed & summary data

Report Design

Report usage/user needs.

Report layout choices.

Paper sizes.

Printer constraints.

How often is it generated?

Events that trigger report?

How large is the report?

Number of copies?

Colors?

Security controls

Output concerns

Report Graphs

Separate query.

Detail

1Locate in detail or group footer section.

2Avoid aggregation and groups in query.

3Include column that links to detail query in report.

Subtotals and totals

1Typically located in report footer or header.2Compare group totals

3Relies on Group By and aggregation.

4Be sure query groups match report groups


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ApplicationApplication Features

Application organization

Menu

Toolbar

Help

Transactions

Improving forms

Customized reports

Distributing Applications

Bad poor & better design

1Bad design:

Enter data twice.

2Poor design:

Memorize data (ID) on one form to enter on second.

3Better design:

Automatically transfer data across forms.

Application Importance:

1- User interface

2- Ensure data integrity

3- Decision Support

4- Expert Systems & Intelligence

Application Organization:

Organized by user needs. Direct users to tasks

Drawbacks

Build forms and reports.

Use menu stubs for incomplete and future work



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Help

On-line help replaces manuals Hypertext links to related topics defined as:

Sequential topics

1Descriptions

2Examples

Definitions / Glossary

Contents / overview

Index / keywords

Full-text search

Accessibility

A design goal to make the application usable by as many users as possible

Aesthetics

An application design goal, where layout, colors, and artwork are used to

improve the appearance

Bound control

A control on a form that is tied to a column in the database. When data is

entered or changed, the changes are automatically saved to the data table.

Check box

A square button that signifies a choice.

Clarity

The goal of making an application easier to use through elegant design and

organization that matches user tasks so that the purpose and use of the

application is clear to the user.

Combo box

A combination of a list box and a text box that is used to enter new data or to

select from a list of items.


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Command button

A button on a form that is designed to be clicked. The designer writes the

code that is activated when the button is clicked.

Consistency

The transaction requirement that specifies all data must remain internally

consistent when changes are committed and can be validated by application

checks.

Context-sensitive menu

A menu that changes depending on the object selected by the user.

ControlsThe generic term for an item placed on a form. Typical controls consist of

text boxes, combo boxes, and labels.

Direct manipulation of objects

A graphical interface method that is designed to mimic real world actions.

Dock able toolbar

A toolbar that users can drag to any location on the application window..

Drag-and-drop

A graphical interface technique where actions are defined by holding down a

mouse key, dragging an icon, and dropping the icon on a new object.

Feedback

A design feature where the application provides information to the user as

tasks are accomplished or errors arise.

Focus

In a window environment, a form or control has focus when it is the one thatwill receive keystrokes. It is usually highlighted.

Group break

A report that splits data into groups. The split-point is called a break. Also

known as a control break.



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Heads-down data entry

Touch typists concentrate on entering data without looking at the screen.

Forms for this task should minimize keystrokes and use audio cues.

Help system

A method for displaying, sequencing, and searching help documentation.

Developers need to write the Help files in a specific format and then use a

Help compiler to generate the final Help file.

Human factors design

An attempt to design computer systems that best accommodate human users.

Hypertext markup language(HTML) A display standard that is used to create documents to be shared on

the Internet. Several generators will create HTML documents from standard

word processor files.

List box

A control on a form that displays a list of choices. The list is always

displayed and takes up a fixed amount of space on the screen.

Menu

A set of application commands grouped togetherusually on a toolbar. It

provides an easy reference for commonly used commands and highlights the

structure of the application.

Modal form

A form that takes priority on the screen and forces the user to deal with it

before continuing. It should be avoided because it interrupts the user.

Option buttonA round button that is used to indicate a choice. By the design guide, option

buttons signify mutually exclusive choices, as opposed to check boxes.

Page footer

A report element that appears at the bottom of every page. Often used for

page numbers.


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Tabular form

An input form that displays data in columns and rows. It is used when there

are few columns of data or when the user needs to see multiple rows at the

same time.

Toolbar

A small object in applications that can hold buttons and text menus. Users

can execute commands with one or two mouse clicks. Used to hold

frequently used commands, and commands that are used across the entire

application, such as printing.

Tool tip

A small object in applications that can hold buttons and text menus. Userscan execute commands with one or two mouse clicks. Used to hold

frequently used commands, and commands that are used across the entire

application, such as printing.

Unicode

A standard method of storing and displaying a variety of character sets.


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Section 7: Triggers & Cursors & Functions

Procedural LanguagesA traditional programming language, where you specify the sequence of a

set of commands.

SQL commands

Rae not procedural language because you tell the DBMS only what you

want done, not how to do it.

Create code

1- Within the query system

2- In forms and reports

3- Hosted in external programs

Looking Up Data

Obtaining data from a single row is straightforward with the SELECT INFO.

- It gets to the variable.

- It has one row.

Data triggers

Code that is executed when some data element is modified.Procedures that are executed when some event arises within the database.

Event:Any process happens.

Note: The common events are Update, Insert, and Delete.

Note: The main data trigger on the row and columns each have two

attributes: BEFORE and AFTER.

Statement versus Row TriggersThe SQL defines two levels of triggers:

1- Triggers may be assigned to the overall table.

2- Triggers may be assigned to fire for each row of data being modified.



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Cascading Triggers

Arise when a change that fire a trigger on one table cause a change in the

second table, that triggers a change in third table, and so on.

Transactions

A set of changes that must all be made together.

The computer needs to be told which changes must be grouped into a

transaction.

1. Turn on transaction processing.

2. Signify a transaction start.3. Signify the end.

Success: save all changes

Failure: cancel all changes

Must be set in module code

Commit

Rollback

SAVEPOINT

Divides transaction procedures into multiple pieces.

Concurrent Access

When two people try to change the same data at the same time.

In this case Final data will be wrong

Pessimistic Locks: Serialization

Serialization

Process forces transactions to run separately so that a second process cannot

even read the data being modified by the first process.

Note: One answer to concurrent access is to prevent it.

When a transaction needs to alter data, it places a SERIALIZABLE lock on

the data used, so no other transactions can even read the data until the first

transaction is completed.


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Deadlock

Arises when two (or more) processes have placed locks on data and are

waiting for the others data.

Many solutions:

- Random wait time

- Global lock manager

- Two-phase commit messages

Optimistic Locks

Begins by assuming that collisions are rare and unlikely to arise.

Improved performance, fewer resources allow all code to read any data (nolocks).

When code tries to write a new value

- Check to see if the existing value is different from the one you were

given earlier

- If it is different, someone changed the database before you finished,

so it is a collision--raise an error

- Reread the value and try again

Atomicity: all changes succeed or fail together.

Consistency: all data remain internally consistent (when committed) and can

be validated by application checks.

Isolation: The system gives each transaction the perception that it is running

in isolation. There are no concurrent access issues.

Durability: When a transaction is committed, all changes are permanently

saved even if there is a hardware or system failure.

Logically, generated keys could be created through two primary methods:

1- By automatic method when a new row is added to a table.

2- By separate key generation routine.



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Database Cursors

Defines a SELECT statement and then point to one row at a time.

A Loop statement enables you to move the cursor to the next row and

repeat your code to examine each row returned by query.

Purpose

Track through table or query one row at a time.

Data cursor is a pointer to active row.

Why?

Performance.

SQL cannot do everything. Complex calculations.

Compare multiple rows.

Atomicity

The transaction element that specifies that all changes in a transaction must

succeed or fail together.

Cascading triggers

Multiple events that arise when a change that fires a trigger on one tablecauses a change in a second table, that triggers a change in a third table and

so on.

Concurrent access

Performing two (or more) operations on the same data at the same time. The

DBMS must sequence the operations so that some of the changes are not

lost.

consistency, application

The goal of making an application easier to use by using the same features,

colors, and commands throughout. Modern applications also strive for

consistency with a common design guide.


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Database cursor

A variable created within a programming language that defines a SELECT

statement and points to one row of data at a time. Data on that row can be

retrieved or edited using the programming language.

Deadlock

A situation that exists when two (or more) processes each has a lock on a

piece of data that the other one needs.

Durability

The transaction element that specifies that when a transaction is committed,

all changes are permanently saved even if there is a hardware or system

failure.

Isolation

The transaction requirement that says the system must give each transaction

the perception that it is running in isolation with no concurrent access issues.

Isolation level

Used to assign locking properties in transactions. At a minimum, it is used to

specify optimistic or pessimistic locks. Some systems support intermediate

levels.

Optimistic lock

A transaction lock that does not block other processes. If the data is changed

between read and write steps, the system generates an error that must be

handled by code.

Persistent stored modules

(PSM) In SQL-99 a proposed method for storing methods associated with

objects. The module code would be stored and retrieved automatically by the

DBMS.

Pessimistic lock

A complete isolation level that blocks other processes from reading a locked

piece of data until the transaction is complete. Program code will receive an

error message if the data element is locked.



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Procedural language

A traditional programming language that is based on following procedures

and is typically executed one statement at a time. Compared to SQL, which

operates on sets of data with one command.

Serialization

A transaction requirement that specifies that each transaction is treated

completely separately and run as if there were no other transactions.

Transaction

In a database application a transaction is a set of changes that must all be

made together. Transactions must be identified to the DBMS and then

committed or rolled back (if there is an error). For example, a transfer of

money from one bank account to another requires two changes to thedatabaseboth must succeed or fail together.

Trigger

An event that causes a procedure to be executed. For example, clicking a

button can be a trigger, as can a change in a data value.

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