1. Algjebra Relacionale & SQL
Ligjerata 2
Algjebra Relacionale & SQL

2. Algjebra Relacionale
Algjebra Relacionale perdoret per te definuar menyren se si relacionet (tabelat) mund te operojne dhe dhe manipulojne me te dhena.
Ajo perdor bazat e SQL me bazen e te dhenave relacionale, dhe ilustron operacionet bazike duke perdore DML.
Kjo algjeber i paraqet operacionet themelore (duke involvuar tabelat) dhe operatcionet binare (duke perdore disa tabela).

3. SQL Structured Query Language (SQL)
Eshte e Standardizuar nga ANSI
Perkrahet nga RDBMS-te moderne
Kommandat jane te perfshira ne tri grupe
Data Definition Language (DLL)
Krijojne tabelat , etj
Data Manipulation Language (DML)
Modifikoojne te dhenat
Data Control Language
Kontrollojne se qka duan te perdorin – pranimet dhe nderprerjen e privilegjet

4. Operacionet Selekcionimi Projektimi

5. Selection
Seleksionimi ose operacioni  selekton rreshtat prej tabeles qe paraqitet me kushtin:
   < kusht > < emri i tabeles>
Shembull:  course = ‘CM’ Students
Students
stud# name course
100 Faton PH stud# name course
200 Agim CM Agim CM
300 Bujar CM Bujar CM

6. Projeksioni
Projekcioni ose  eshte operacion i cili selekton listen e kolonave nga tabela.
 < lista e kolones > < emriitabeles >
shembulli:  stud#, name Students
Students
stud# name course stud# name
100 Faton PH Faton
Agim CM Agim
Bujar CM Bujar

7. Selekcionimi / Projektimi
Selekcionimi dhe projektimi zakonisht kombinohen:
 stud#, name ( course = ‘CM’ Students)
Students
stud# name course
100 Faton PH stud# name
200 Agim CM Agim
300 Bujar CM Bujar

8. Operacionet Binare Cartesian Product Theta Join Inner Join Natural Join Outer Joins Semi Joins

9. Produkti Cartesian
Çdo rresht në relacionin e parë (R) me çdo rresht në lidhje të dytë (S):
R X S

10. Produkti Cartesian - Shembull
Students Courses
stud# name course course# name
100 Faton PH PH Pharmacy
200 Agim CM CM Computing
300 Bujar CM
Students X Courses =
stud# Students.name course course# Courses.name
100 Faton PH PH Pharmacy
100 Faton PH CM Computing
200 Agim CM PH Pharmacy
200 Agim CM CM Computing
300 Bujar CM PH Pharmacy
300 Bujar CM CM Computing

11. Theta Join
Produkti Kartezian me kusht aplikohet:
R ⋈ <kushti> S

12. Theta Join - Shembull Students Courses stud# name course course# name
100 Faton PH PH Pharmacy
200 Agim CM CM Computing
300 Bujar CM
Students ⋈ stud# = 200 Courses
stud# Students.name course course# Courses.name
200 Agim CM PH Pharmacy
200 Agim CM CM Computing

13. Inner Join (Equijoin) brendshem
Theta join ku <kushti> eshte (=) per qelesin primar dhe qelesin e jashtem
R ⋈ <R.primary_key = S.foreign_key> S

14. Inner Join - Shembull Students Courses stud# name course course# name
100 Faton PH PH Pharmacy
200 Agim CM CM Computing
300 Bujar CM
Students ⋈ course = course# Courses
stud# Students.name course course# Courses.name
100 Faton PH PH Pharmacy
200 Agim CM CM Computing
300 Bujar CM CM Computing

15. Natural Join
Inner join jep te dhena te teperta (ne shembullin e meparshem: course and course#). Për të hequr këtë dyfishim:
 < stud#, Students.name, course, Courses.name >
(Students ⋈ <course = course#> Courses)
Ose
R1= Students ⋈ <course = course#> Courses
R2=  < stud#, Students.name, course, Courses.name > R1
Rezultati quhet natural join i Students dhe Courses

16. Natural Join - Shembull
Students Courses
stud# name course course# name
100 Faton PH PH Pharmacy
200 Agim CM CM Computing
Bujar CM
R1= Students ⋈ <course = course#> Courses
R2=  < stud#, Students.name, course, Courses.name > R1
stud# Students.name course Courses.name
100 Faton PH Pharmacy
200 Agim CM Computing
300 Bujar CM Computing

17. Outer Joins
Inner join + rreshat e tabeles qe nuk e plotesojne <kushtin>
Left Outer Join: R <R.primary_key = S.foreign_key> S
Të gjitha rreshtave nga R ruhen dhe rreshtat tjere e S janë
te mbushur me NULL
Right Outer Join: R <R.primary_key = S.foreign_key> S
Të gjitha rreshtave nga S ruhen dhe rreshtave qe nuk e plotesojne kushtin në R janë te mbushura me NULL

18. Left Outer Join - Shembull
Students Courses
stud# name course course# name
100 Faton PH PH Pharmacy
200 Agim CM CM Computing
Petrit EN CH Chemistry
Students <course = course#> Courses
stud# Students.name course course# Courses.name
100 Faton PH PH Pharmacy
200 Agim CM CM Computing
Petrit EN NULL NULL

19. Right Outer Join - Shembull
Students Courses
stud# name course course# name
100 Faton PH PH Pharmacy
200 Agim CM CM Computing
Petrit EN CH Chemistry
Students <course = course#> Courses
stud# Students.name course course# Courses.name
Faton PH PH Pharmacy
Agim CM CM Computing
NULL NULL NULL CH Chemistry

20. Kombinimi i operacioneve dhe JOIN
Students Courses
stud# name address course course# name
100 Faton Aberdeen PH PH Pharmacy
200 Agim Dundee CM CM Computing
300 Bujar Aberdeen CM
Si te paraqiten emrat e studenteve (nga Aberdeen) dhe emrat e kursev ete tyre
R1= Students ⋈ <course=course#> Courses
R2=  <address=“Aberdeen”> R1
R3=  <Students.name, Course.name> R2
Students.name Courses.name
Faton Pharmacy
Bujar Computing

21. Disa Operacione te tjera
Unioni
Intersekcioni
Diferenca

22. Unioni
Takes the set of rows in each table and combines them, eliminating duplicates
Participating relations must be compatible, ie have the same number of columns, and the same column names, domains, and data types
R S R  S
A B
a2 b2
a3 b3
A B
a1 b1
a2 b2
a3 b3
A B
a1 b1
a2 b2

23. Intersection Takes the set of rows that are common to each relation
Participating relations must be compatible
R S R  S
A B
a1 b1
a2 b2
A B
a2 b2
a3 b3
A B
a2 b2

24. Difference
Takes the set of rows in the first relation but not the second
Participating relations must be compatible
R S R - S
A B
a1 b1
a2 b2
A B
a2 b2
a3 b3
A B
a1 b1

25. Ushtrimi - Employee WorkLoad Project
empid name empid* projid* duration projid name
E100 Faton E100 P P001 DB
E200 Agim E200 P P002 Access
E300 Bujar E300 P P003 SQL
E400 Petrit
Përcaktoni rezultatin e operacioneve për:
Natural join ndermjet Employee dhe WorkLoad
Left outer join ndermjet Employee dhe WorkLoad
Right outer join ndermjet WorkLoad dhe Project

26. Algjebra Relacionale Te shkruarit e oeracioneve ne SQL

27. Unary Operations Selection Projection  course = ‘Computing’ Students
In SQL:
Select *
From Students
Where course = ‘Computing’;
Projection
 stud#, name Students
In SQL:
Select stud#, name
From Students;
Selection & Projection
 stud#, name ( course = ‘Computing’ Students)
In SQL:
Select stud#, name
From students
Where course = ‘Computing’;

28. Binary Operations/Joins
Cartesian Product: Students X Courses
In SQL:
Select *
From Students, Courses;
Theta Join: Students ⋈ <stud# =200> Courses
In SQL:
Select *
From Students, Courses
Where stud# = 200;

29. Binary Operations/Joins
Inner Join (Equijoin): Students ⋈ <course=course#> Courses
In SQL:
Select *
From Students, Courses
Where course=course#;
Natural Join:
R1= Students ⋈ <course = course#> Courses
R2=  < stud#, Students.name, course, Courses.name > R1
In SQL:
Select stud#, Students.name, course, Courses.name
From Students, Courses
Where course=course#;

30. Outer Joins Left Outer Join Students <course = course#> Courses
In SQL:
Select *
From Students, Courses
Where course = course#(+)
Right Outer Join
Students <course = course#> Courses
In SQL:
Select *
From Students, Courses
Where course(+) = course#

31. Combination of Unary and Join Operations
R1= Students ⋈ <course=course#> Courses
R2=  <address=“Aberdeen”> R1
R3=  <Students.name, Course.name> R2
In SQL:
Select Students.name, Courses.name
From Students, Courses
Where course=course#
AND address=“Aberdeen”;

32. Set Operations Union: R  S Intersection: R  S In SQL: In SQL:
Select * From R
Union
Select * From S;
Intersection: R  S
In SQL:
Select * From R
Intersect
Select * From S;
Difference: R - S
In SQL:
Select * From R
Minus
Select * From S;

33. SQL Operators
Between, In, Like, Not

34. SQL Operators SELECT * FROM Book WHERE catno BETWEEN 200 AND 400;
FROM Product
WHERE prod_desc BETWEEN ‘C’ AND ‘S’;
WHERE catno NOT BETWEEN 200 AND 400;

35. SQL Operators SELECT Catno FROM Loan WHERE Date-Returned IS NULL;
WHERE Date-Returned IS NOT NULL;

36. SQL Operators SELECT Name FROM Member
WHERE memno IN (100, 200, 300, 400);
WHERE memno NOT IN (100, 200, 300, 400);

37. SQL Operators SELECT Name FROM Member
WHERE address NOT LIKE ‘%Aberdeen%’;
WHERE Name LIKE ‘_ES%’;
Note: In MS Access, use * and # instead of % and _

38. Selecting Distinct Values
Student
stud# name address
100 Faton Aberdeen
200 Agim Dundee
300 Bujar Aberdeen
SELECT Distinct address
FROM Student;
address
Aberdeen
Dundee

39. Exercise Employee(empid, name) Project(projid, name)
WorkLoad(empid*, projid*, duration)
List the names of employees working on project
name ‘Databases’.