aplikime te bazave te te dhenave 2
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Prof Dr Ermir Rogovaermir.rogova@uni-prizren.com
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mailto:ermir.rogova@uni-prizren.commailto:ermir.rogova@uni-prizren.commailto:ermir.rogova@uni-prizren.commailto:ermir.rogova@uni-prizren.com -
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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 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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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 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 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 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 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
sid name login age gpa
53666 Jones jones@cs 18 3.4
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 sensitiveEffect 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:vkwong@iusb.edumailto:vkwong@iusb.eduhttp://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
FemaleOutput
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:
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