Techniques for Manipulating Relational Data - Data Base Management System - Lecture Slides, Slides of Database Management Systems (DBMS)

Download Techniques for Manipulating Relational Data - Data Base Management System - Lecture Slides and more Slides Database Management Systems (DBMS) in PDF only on Docsity! Techniques for Manipulating Relational Data Docsity.com Definition Terms • DDL (data definition language) - of a relational system is used to define the database’s attributes, tables, relationships, and indexes. • DML (data manipulation language) – is used to extract, insert, and modify the information content of the database. Docsity.com What does relational algebra operators do? • Reduce the number of tuples in a set by selecting those that satisfy some criteria (selection operators). • Reduce the size of each tuple in a set by eliminating specific attributes (projection operators). • Manipulate two similar sets of tuples by combining or comparing (set operators). • Increase the size of each tuple by adding attributes (join and product operations). Docsity.com Find all customers whose last name is “Doe” Customer account id last Name first Name street city state zipcode balance 101 Block Jane 345 R Cir. Apopka FL 30458- $0.00 102 Hamilton Cherry 3230 D St. Dade City FL 30555- $3.00 103 Harrison Katherine 103 L Hall Bratt FL 30457- $31.00 104 Breaux Carroll 76 M St. Apopka FL 30458- $35.00 106 Morehouse Anita 9501 L St. Houma LA 44099- $0.00 111 Doe Jane 123 M St. Apopka FL 30458- $0.00 201 Greaves Joseph 14325 N St. Godfrey IL 43580- $0.00 444 Doe Jane D rm 142 Tallahassee FL 32306- $10.55 Docsity.com Using selection operator to solve the previous task • Relational algebra expression would be σlastName=‘DOE’(Customer) • The new relation results from a selection that has the same attributes as the input relation, but may have fewer rows. Docsity.com Using selection operator to solve previous task • Relational algebra expression would be σssn=‘376-77-0099’ and date > ’01-mar-1999’(TimeCard) • The new relation results from a selection that has the same attributes as the input relation, but may have fewer rows. Docsity.com Result of finding all employees whose ssn is 376- 77-0099 and who were employed after march 1, 1998 ssn date startTime endTime storeId paid 376-77-0099 2/23/1999 14:00 22:00 5 yes 376-77-0099 1/3/1999 10:00 14:00 5 yes 376-77-0099 1/3/1999 15:00 19:00 5 yes Docsity.com List the first and last names of all customers Customer account id last Name first Name street city state zipcode balance 101 Block Jane 345 R Cir. Apopka FL 30458- $0.00 102 Hamilton Cherry 3230 D St. Dade City FL 30555- $3.00 103 Harrison Katherine 103 L Hall Bratt FL 30457- $31.00 104 Breaux Carroll 76 M St. Apopka FL 30458- $35.00 106 Morehouse Anita 9501 L St. Houma LA 44099- $0.00 111 Doe Jane 123 M St. Apopka FL 30458- $0.00 201 Greaves Joseph 14325 N St. Godfrey IL 43580- $0.00 444 Doe Jane D rm 142 Tallahassee FL 32306- $10.55 Docsity.com What are Set Operators? • When two relations have the same shape, that is, when the types of the attributes are the same, we can apply the usual set operators to the relations. • This includes union, intersection, and difference. Docsity.com Explanation of Set Operators • The union of two relations is a relation that contains the set of each tuple that is in at least one of the input relations. • The intersection of two relations is the set of all tuples that occur in both input relations. • The difference between two relations is the set of all tuples that are in the first relation but not in the second. Docsity.com Set Operator Examples R 3 Rx a 4 a] b 2 = a]l2 3 a] 3 b]1 b] 2 b] 3 (8) Selection (b) Projection (c) Cartesian product RESTRICTION RUS RNS R-S& R [| R | | &§ § (d) Union {2} Intersection (f) Set difference Docsity.com Partial Result of σEmployee.ssn=TimeCard.ssn(Employee X TimeCard) Employee. ssn lastName firstNa me TimeCard. ssn date startTim e endTim e storeId paid 145-09- 0967 Uno Jane 145-09- 0967 1/14/1999 8:15 12:00 3 no 245-11- 4554 Toulouse Jie 245-11- 4554 1/14/1999 8:15 12:00 3 no 145-09- 0967 Uno Jane 376-77- 0099 2/23/1999 14:00 22:00 5 no 245-11- 4554 Toulouse Jie 145-09- 0967 1/14/1999 8:15 12:00 3 no Docsity.com Join operators • It is expressed as those rows in the product whose specified fields match. • It puts together related objects from two relations. Docsity.com Employee natural joinssn TimeCard Employee ssn lastName firstName 145-09-0967 Uno Jane 245-11-4554 Toulouse Jennifer 376-77-0099 Threat Ayisha 479-98-0098 Fortune Bruce 588-99-0093 Fivozinsky Bruce TimeCard ssn date startTime endTime storeId paid 145-09-0967 1/14/1999 8:15 12:00 3 yes 245-11-4554 1/14/1999 8:15 12:00 3 yes 376-77-0099 2/23/1999 14:00 22:00 5 yes 145-09-0967 1/16/1999 8:15 12:00 3 yes 376-77-0099 1/3/1999 10:00 14:00 5 yes 376-77-0099 1/3/1999 15:00 19:00 5 yes Docsity.com