Aplikime Te Bazave Te Te Dhenave 2

7/28/2019 Aplikime Te Bazave Te Te Dhenave 2

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Prof Dr Ermir [email protected]

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mailto:[email protected]:[email protected]:[email protected]:[email protected]


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SQL: standard language Data Definition Language (DDL)

create, modify, delete tables

specify constraints

administer users, security, etc.

Data Manipulation Language (DML) Specify queries to find tuples that satisfy criteria

add, modify, remove tuples

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CREATE TABLE ( , )

INSERT INTO ()VALUES ()

DELETE FROM WHERE

UPDATE SET =

WHERE

SELECT FROM

WHERE

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Creates the Students table. Note: the type (domain) of

each field is specified, andenforced by the DBMS

whenever tuples are added or

modified.

Another example: the Enrolledtable holds information aboutcourses students take.

CREATE TABLE Students(sid CHAR(20),name CHAR(20),login CHAR(10),

age INTEGER,gpa FLOAT)

CREATE TABLE Enrolled(sid CHAR(20),cid CHAR(20),grade CHAR(2))

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Can insert a single tuple using:

INSERT INTO Students (sid, name, login, age, gpa)VALUES (53688, Smith, smith@ee, 18, 3.2)

Can delete all tuples satisfying some condition(e.g., name = Smith):

DELETEFROM Students SWHERES.name = Smith

Powerful variants of these commands are available;more later! 5


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Keys are a way to associate tuples in differentrelations

Keys are one form of integrity constraint (IC)

sid name login age gpa

53666 Jones jones@cs 18 3.4

53688 Smith smith@eecs 18 3.2

53650 Smith smith@math 19 3.8

sid cid grade

53666 Carnatic101 C

53666 Reggae203 B53650 Topology112 A

53666 History105 B

EnrolledStudents

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A Foreign Key is a field whose values are keysin another relation.





sid cid grade

53666 Carnatic101 C

53666 Reggae203 B53650 Topology112 A

53666 History105 B

EnrolledStudents

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Foreign key: Set of fields in one relation that isused to `refer to a tuple in another relation.

Must correspond to primary key of the secondrelation.

Like a `logical pointer.

E.g. sidis a foreign key referring to Students:

Enrolled(sid: string, cid: string,grade: string) If all foreign key constraints are enforced, referential

integrityis achieved (i.e., no dangling references.)

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Only students listed in the Students relation shouldbe allowed to enroll for courses.

CREATE TABLE Enrolled(sid CHAR(20), cid CHAR(20), grade CHAR(2),PRIMARY KEY (sid,cid),FOREIGN KEY (sid) REFERENCES Students )





sid cid grade

53666 Carnatic101 C

53666 Reggae203 B

53650 Topology112 A

53666 History105 B

EnrolledStudents

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IC: condition that must be true for anyinstanceof the database; e.g., domain constraints. ICs are specified when schema is defined.

ICs are checked when relations are modified. A legalinstance of a relation is one that

satisfies all specified ICs. DBMS should not allow illegal instances.

If the DBMS checks ICs, stored data is morefaithful to real-world meaning. Avoids data entry errors, too!

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Remember Students and Enrolled; sidin Enrolled is a foreign key thatreferences Students.

What should be done if an Enrolled tuple with a non-existent student id isinserted? (Reject it!)

What should be done if a Students tuple is deleted? Also delete all Enrolled tuples that refer to it.

Disallow deletion of a Students tuple that is referred to. Set sid in Enrolled tuples that refer to it to a default sid. (In SQL, also: Set sid in Enrolled tuples that refer to it to a special value null,

denoting `unknownor `inapplicable.) Similar if primary key of Students tuple is updated.





sid cid grade

53666 Carnatic101 C

53666 Reggae203 B

53650 Topology112 A53666 History105 B

Enrolled Students

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The most widely used relational querylanguage.

Current std is SQL99; SQL92 is a basic subset

To find all 18 year old students, we can write:SELECT *FROM Students SWHERE S.age=18

To find just names and logins, replace the first line:

SELECT S.name, S.login



53688 Smith smith@ee 18 3.2

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What does the following query compute?SELECT S.name, E.cidFROM Students S, Enrolled EWHERE S.sid=E.sid AND E.grade='A'

S.name E.cid

Smith Topology112

sid cid grade

53831 Carnatic101 C

53831 Reggae203 B

53650 Topology112 A53666 History105 B

Given the following instance ofEnrolled

we get:

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Hyper Text Markup Language A markup language designed for the creation

of web pages and other information viewablein a browser The basic language used to write web pages File extension: .htm, .html


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1. Open Notepad2. Click on File -> Save as3. In the File name pull-down box, type in

webpage.html4. Click on Save5. Type in content for your file

6. Once you finished the content, click on File -> Save


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For example: , ,,

etc. Tag usually goes with pair: an open tag () and

an end tag ()

Single tag: ,
Tags are NOT case sensitive

Effect Code Code Used What It Does

Bold B Bold Bold

Italic I Italic Italic


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Page Title Goes Here

content goes here


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Bgcolor Specifies a background-

color for a HTML page.

Background Specifies a background-

image for a HTML page


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Put text on a webpage

Today is my first day at my new job, Im so

excited!

Output: Today is my first day at my new job, Im so excited!

Put text in center of a page Hello

Output: Hello

Put text on the right of a page

Hello
Output: Hello


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To change text size Hello

Output: Hello

To change text color Hello

Output: Hello

Using both Hello

Output: Hello

Tag attribute


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There are 6 heading commands.

This is Heading 1

This is Heading 2

This is Heading 3

This is Heading 4

This is Heading 5

This is Heading 6


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Unordered list

Code:

CoffeeMilk

Output:

Coffee Milk

Ordered list

Code:

CoffeeMilk

Output:

1. Coffee2. Milk


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A Hypertext link

< a href=http://www.iusb.edu>IUSB Home

Output: IUSB Home

A Email link

Email me Output: Email me
http://www.iusb.edu/mailto:[email protected]:[email protected]://www.iusb.edu/


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.gif

Graphics Interchange Format

.jpeg or .jpg Joint Photographic Experts Group

.bmp

bitmap


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Computer images are made up of pixels

Width

Height


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A form is an area that can contain formelements.

Commonly used form elements includes:

Text fields

Radio buttons

Checkboxes

Submit buttons


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When user clicks on theSubmit button, thecontent of the form is sentto another file.

Username:

Output

Username:


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Used when you want theuser to select one or moreoptions of a limitednumber of choices.

Ihave a car

Output

I have a bikeI have a car


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Used when you want theuser to select one of alimited number of choices.

Male
Female

Output

MaleFemale


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Used when you want to getinput from user.

Please provide your

suggestion in the text boxbelow:

Output

Please provide yoursuggestion in the text box

below:


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Used when you want userto respond with onespecific answer withchoices you given.

Select a fruit:
Apples Bananas
< option > Oranges

Output

Select a fruit:

Aplikime Te Bazave Te Te Dhenave 2

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