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![Precedence of relational operators:
1.[SELECT, PROJECT, RENAME]
(highest).
2.[PRODUCT, JOIN].
3.INTERSECTION.
4.[UNION, --]
prepared by Visakh V,Assistant Professor,
LBSITW](https://image.slidesharecdn.com/relationalalgebracomplete-190326063216/75/Relational-algebra-complete-67-2048.jpg)
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Relational algebra complete
This document discusses relational algebra, which provides a formal foundation for the relational model of databases. It describes several key relational algebra operations including selection, projection, join, union, intersection, difference, and cartesian product. Selection allows retrieving rows that satisfy a given condition. Projection selects certain columns. Join combines related tuples from two relations. Set operations like union, intersection, and difference are also covered. The document provides examples to illustrate how each operation works and can be used to solve retrieval queries. Relational algebra operations form the basis for implementing and optimizing queries in relational database management systems.
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Relational algebra complete
- 1. Relational Algebra prepared by VisakhV,Assistant Professor, LBSITW
- 2. prepared by VisakhV,Assistant Professor, LBSITW
- 3. prepared by VisakhV,Assistant Professor, LBSITW
- 4. •Two formal languagefor the relational model (a)Relational Algebra (b)Relational calculus prepared by Visakh V,Assistant Professor, LBSITW
- 5. • Basic setof operation for the relational model. • These operation enable a user to specify basic retrieval requests. • The result of a retrieval is a new relation, which can be further manipulated using operations of same algebra. prepared by Visakh V,Assistant Professor, LBSITW
- 6. •it is importantfor several reasons: provides formal foundation for relational model used as basis for implementing and optimizing queries in RDMS Some of its concepts are incorporated into SQL Standard query language for RDMS prepared by Visakh V,Assistant Professor, LBSITW
- 7. No commercial RDBMSin use today provides an interface for the relational queries. •Relational algebra operations can be divided into UNION INTERSECTION SET DIFFERENCE CARTESIAN PRODUCT SELECT PROJECT JOIN etc. prepared by Visakh V,Assistant Professor, LBSITW
- 8. prepared by VisakhV,Assistant Professor, LBSITW
- 9. s p :Operate on asingle relation prepared by Visakh V,Assistant Professor, LBSITW
- 10. s prepared by VisakhV,Assistant Professor, LBSITW
- 11. Syntax : s <selectioncondition> (R) <selection condition> is made up of number of clauses of the form <attribute name > <comparison op> <attribute name> OR <attribute name > <comparison op> <constant value> { =,<,>,<=,>=,!= } It select certain rows prepared by Visakh V,Assistant Professor, LBSITW
- 12. prepared by VisakhV,Assistant Professor, LBSITW
- 13. Ex : s(DNO=5) (EMPLOYEE) Ex : s(SALARY>25000) (EMPLOYEE) Lets try. . . prepared by Visakh V,Assistant Professor, LBSITW
- 14. Clauses can beconnected by the Boolean operators and, or ,not to from a general selection condition. s(DNO=4 AND SALARY>25000) OR (DNO=5 AND SALARY>30000) (EMPLOYEE) prepared by Visakh V,Assistant Professor, LBSITW
- 15. SELECT operation iscommutative : s <cond1> ( s <cond2> (R)) = s <cond2> ( s <cond1> (R)) Cascade of SELECT operation: s<cond1> ( s <cond2> (… ( s <condn> (R)). . . )) = ( s <cond1> AND <cond2> AND . . . AND <condn> (R) prepared by Visakh V,Assistant Professor, LBSITW
- 16. p prepared by VisakhV,Assistant Professor, LBSITW
- 17. Syntax : p <attributelist > (R) It select certain columns Duplicate elimination : it removes any duplicate tuples , and we get a valid relation . prepared by Visakh V,Assistant Professor, LBSITW
- 18. prepared by VisakhV,Assistant Professor, LBSITW
- 19. •pSEX, SALARY(EMPLOYEE) •pLname,Fname,SALARY(EMPLOYEE) Where isthe resultant table ??? prepared by Visakh V,Assistant Professor, LBSITW
- 20. Duplicate elimination pFNAME, LNAME, SALARY(sDNO=5(EMPLOYEE)) preparedby Visakh V,Assistant Professor, LBSITW
- 21. prepared by VisakhV,Assistant Professor, LBSITW
- 22. We can writethe operations as a single algebra expression by nesting the operation or we can apply one operation at a time and create intermediate result relations. pFNAME, LNAME, SALARY(sDNO=5(EMPLOYEE)) Can replace with DEPCS2 sDNO=5(EMPLOYEE) RESULT pFNAME, LNAME, SALARY (DEPCS2) prepared by Visakh V,Assistant Professor, LBSITW
- 23. Renaming of attribute TEMP sDNO=5(EMPLOYEE) R(FIRSTNAME,LASTNAME,SALARY) pFNAME, LNAME, SALARY (TEMP) prepared by Visakh V,Assistant Professor, LBSITW
- 24. A formal RENAMEr(rho) operations: • rename either relation name, attribute name or both r (B1,B2,…Bn) (R) r s (R) r s(B1,B2,…Bn) (R) S: new table name; Bn: new attribute name prepared by Visakh V,Assistant Professor, LBSITW
- 25. prepared by VisakhV,Assistant Professor, LBSITW
- 26. UNION INTERSECTION & SET DIFFERENCE prepared byVisakh V,Assistant Professor, LBSITW
- 27. : R S : Include all tuples :Duplicates are eliminated : R S : include all tuples that are in both R & S : R - S : include all tuples that are in R but not in S prepared by Visakh V,Assistant Professor, LBSITW
- 28. Union compatible (corresponding pairhave same number of attribute and same domain) prepared by Visakh V,Assistant Professor, LBSITW
- 29. prepared by VisakhV,Assistant Professor, LBSITW
- 30. prepared by VisakhV,Assistant Professor, LBSITW
- 31. Example: prepared by VisakhV,Assistant Professor, LBSITW
- 32. Q. Retrieve thesocial security Number of all employees who either work in department 5 or directly supervise an employee who works department 5. prepared by Visakh V,Assistant Professor, LBSITW
- 33. prepared by VisakhV,Assistant Professor, LBSITW
- 34. •UNION and INTERSECTIONare commutative but SET DIFFERENCE is not. R S =R S – (R-S )-(S-R) prepared by Visakh V,Assistant Professor, LBSITW
- 35. • Also knownas CROSS PRODUCT or CROSS JOIN • Denoted by X • syntax : • tab1 X tab2 • also binary set operations. • if A has m tuples and B has n tuples then A X B has m * n tuples . • Cartesian product followed by SELECT is used to identify and select related tuples from two relation. prepared by Visakh V,Assistant Professor, LBSITW
- 36. prepared by VisakhV,Assistant Professor, LBSITW
- 37. EMP_ID DESIGNATION SALARY 101PROFESSOR 1,25000 102 ASSOCIATE PROF 90000 103 ASSISTANT PROF 40000 E_ID F_NAME M_NA ME L_NAME AGE 102 SURESH KUMAR S 43 103 SUMI M MOL 23 101 SHREELEKSHMI R S 40 TAB1 FIND salary ,name AND designation OF EACH EMPLOYEE????? prepared by Visakh V,Assistant Professor, LBSITW
- 38. DESIGNATIO N SALARY EMP_I D E_ID F_NAMEM_NAME L_NAM E AGE PROFESSOR 1,25000 101 102 SURESH KUMAR S 43 PROFESSOR 1,25000 101 103 SUMI M MOL 23 PROFESSOR 1.25000 101 101 SHREELEKSHMI R S 40 ASSOCIATE PROF 90000 102 102 SURESH KUMAR S 43 ASSOCIATE PROF 90000 102 103 SUMI M MOL 23 ASSOCIATE PROF 90000 102 101 SHREELEKSHMI R S 40 ASSISTANT PROF 40000 103 102 SURESH KUMAR S 43 ASSISTANT PROF 40000 103 103 SUMI M MOL 23 ASSISTANT PROF 40000 103 101 SHREELEKSHMI R S 40prepared by Visakh V,Assistant Professor, LBSITW
- 39. DESIGNATI ON SALARY EMP_ID E_IDF_NAME M_NAME L_NAME AGE PROFESSO R 1.25000 101 101 SHREELEK SHMI R S 40 ASSOCIATE PROF 90000 102 102 ANIL S GANESH 28 ASSISTANT PROF 40000 103 103 SUMI M MOL 23 SALARY F_NAME M_NAME L_NAME DESIGNATION 1.25000 RAMESH R VINOD PROFESSOR 90000 ANIL S GANESH ASSOCIATE PROF 40000 SUNIL A NARAYAN ASSISTANT PROFprepared by Visakh V,Assistant Professor, LBSITW
- 40. Write relational algebraexpression Retrieve a list of names of each employee’s dependents. prepared by Visakh V,Assistant Professor, LBSITW
- 41. prepared by VisakhV,Assistant Professor, LBSITW
- 42. • Combine relatedtuples from two relation into single tuples. • denoted by • R <JOIN CONDITION> S . • Consider example RESULT EMPLOYEE X DEPENDENT FINAL sSSN= ESSN (RESULT) The above can be replaced with FINAL EMPLOYEE SSN=ESSN DEPENDENT .prepared by Visakh V,Assistant Professor, LBSITW
- 43. Retrieve the nameof manager of each department prepared by Visakh V,Assistant Professor, LBSITW
- 44. prepared by VisakhV,Assistant Professor, LBSITW
- 45. • A generaljoin condition is of the form <condition>AND<condition>AND. . . AND <condition> Each condition of the form Ai Bi ᶱ Comparison operator {=,!=,<,>,<=,>=} •A JOIN operation with such a general join condition is called a THETA JOIN prepared by Visakh V,Assistant Professor, LBSITW
- 46. prepared by VisakhV,Assistant Professor, LBSITW
- 47. • The JOINwhere the only comparison operator used is ‘ = ‘ • It requires that two JOIN attributes have the same name in both relation . • if this is not the case then renaming operation done first. • This is basically an EQUIJOIN followed by removal of unnecessary attributes •Ex: DEPT_LOCS DEPARTMENT * DEPT_LOCATIONS. prepared by Visakh V,Assistant Professor, LBSITW
- 48. Join attribute prepared byVisakh V,Assistant Professor, LBSITW
- 49. •A JOIN operationused to combine data from multiple relations so that related information can be presented in a single table. This operations are also known as inner joins. prepared by Visakh V,Assistant Professor, LBSITW
- 50. • Used whenwe want to keep all the tuples in R • three main variation are • LEFT OUTER JOIN • RIGHT OUTER JOIN • FULL OUTER JOIN prepared by Visakh V,Assistant Professor, LBSITW
- 51. • Relation instructor1 •Relation teaches1 ID course_id 10101 12121 76766 CS-101 APL-101 BIO-101 Comp. Sci. Applied PED ID dept_name 10101 12121 15151 name Sreejith Suresh Sreeja prepared by Visakh V,Assistant Professor, LBSITW
- 52. • Join instructor teaches IDdept_name 10101 12121 Comp. Sci. Applied course_id CS-101 APL-201 name Sreejith Suresh prepared by Visakh V,Assistant Professor, LBSITW
- 53. Left OuterJoin instructor teaches ID dept_name 10101 12121 15151 Comp. Sci. Applied PED course_id CS-101 APL-201 null name Sreejith Suresh Sreeja ID course_id 10101 12121 76766 CS-101 APL-101 BIO-101 Comp. Sci. Applied PED ID dept_name 10101 12121 15151 name Sreejith Suresh Sreeja prepared by Visakh V,Assistant Professor, LBSITW
- 54. Right OuterJoin instructor teaches ID dept_name 10101 12121 76766 Comp. Sci. Applied null course_id CS-101 APL-201 BIO-101 name Sreejith Suresh null ID course_id 10101 12121 76766 CS-101 APL-101 BIO-101 Comp. Sci. Applied PED ID dept_name 10101 12121 15151 name Sreejith Suresh Sreeja prepared by Visakh V,Assistant Professor, LBSITW
- 55. Full OuterJoin instructor teaches ID dept_name 10101 12121 15151 76766 Comp. Sci. Applied PED null course_id CS-101 APL-201 null BIO-101 name Sreejith Suresh Sreeja null ID course_id 10101 12121 76766 CS-101 APL-101 BIO-101 Comp. Sci. Applied PED ID dept_name 10101 12121 15151 name Sreejith Suresh Sreeja prepared by Visakh V,Assistant Professor, LBSITW
- 56. Additional • semi join •left semi join. • Right semi join: Rno Name AGE 1 A 40 2 B 42 3 C 38 R_no Phone 1 9865321245 3 9764316598 5 9598946532 prepared by Visakh V,Assistant Professor, LBSITW
- 57. •left semi join. •Right semi join: Rno Name AGE 1 Mahati 40 3 Meenu 38 R_no Phone 1 9865321245 3 9764316598 prepared by Visakh V,Assistant Professor, LBSITW
- 58. •Denoted by preparedby Visakh V,Assistant Professor, LBSITW
- 59. R S prepared byVisakh V,Assistant Professor, LBSITW
- 60. YEAR TOUR_PART_EM_ID 2003 1001 20041001 2013 1001 2008 1003 2009 1003 2008 1004 2004 1004 2011 1004 2003 1004 2003 1002 2004 1002 2011 1002 2013 1002 2012 1002 EMP_id NAME ADDRESS 1001 SURESH AAAA 1002 LALAN BBBB 1003 JC CCCC 1004 ANVAR DDDD Retrieve the name & address of employees who participated in all tour that ‘Suresh ‘sir attended . prepared by Visakh V,Assistant Professor, LBSITW
- 61. Retrieve the namesof employees who work on all the project that ‘John Smith’ works on prepared by Visakh V,Assistant Professor, LBSITW
- 62. prepared by VisakhV,Assistant Professor, LBSITW
- 63. prepared by VisakhV,Assistant Professor, LBSITW
- 64. • allowing functionsof attributes to be included in the projection •EX: •pSALARY-DEDUCTION, SALARY * 0.25(sDNO=5(EMPLOYEE)) prepared by Visakh V,Assistant Professor, LBSITW
- 65. • SUM •AVERAGE •MAXIMUM •MINIMUM •COUNT •Aggregate functionoperation using the symbol <grouping attribute> <function list>(R) Calligraphic G prepared by Visakh V,Assistant Professor, LBSITW
- 66. a. r R(DNO,NO_OF_EMPLOYEES,AVERAGE_SAL)(Dno COUNT ssn, AVERAGE salary(EMPLOYEE)) b. Dno COUNT ssn, AVERAGE salary(EMPLOYEE) c. COUNT ssn, AVERAGE salary(EMPLOYEE) prepared by Visakh V,Assistant Professor, LBSITW
- 67. Precedence of relationaloperators: 1.[SELECT, PROJECT, RENAME] (highest). 2.[PRODUCT, JOIN]. 3.INTERSECTION. 4.[UNION, --] prepared by Visakh V,Assistant Professor, LBSITW