Announcements Reading for Friday –4.7 – 4.10 Homework 3 – Due 10/1 Project: Steps 2.1-2? –Due 10/4 Exam 1 – 10/6

Relational Data Manipulation Languages Lecture 8

Types of Relational Data Manipulation Languages Procedural: proscriptive - user tells system how to manipulate data - e.g. relational algebra Non-procedural: declarative - user tells what data is needed, not how to get it - e.g. relational calculus, SQL Other types: –Graphical: user provides illustration of data needed e.g. Query By Example(QBE) –Fourth-generation: 4GL uses user-friendly environment to generate custom applications –Natural language: 5GL accepts restricted version of English or other natural language

Relational Algebra Theoretical language with operators that apply to one or two relations to produce another relation Both operands and results are tables Can assign name to resulting table (rename) SELECT, PROJECT, JOIN allow many data retrieval operations

SELECT Operation Applied to a single table, returns rows that meet a specified predicate, copying them to new table SELECT tableName WHERE condition [GIVING newTableName] Symbolically, [newTableName = ]  predicate (table-name) Result table is horizontal subset of operand

PROJECT Operator Operates on single table PROJECT tableName OVER (colName,...,colName) [GIVING newTableName] Symbolically [newTableName =]  colName,...,colName (tableName)

Combining SELECT and PROJECT Can compose SELECT and PROJECT, using result of first as argument for second

Product Binary operations – apply to two tables Product: –

Theta-join THETA join:

Equi-join and Natural Join EQUIJOIN – NATURAL JOIN

Division Binary operator where entire structure of one table (divisor) is a portion of structure of the other (dividend)

Division Example (Club ÷ Stu) ClubNameStuNum ber StuLast Name ComputingS1001Smith ComputingS1002Chin DramaS1001Smith DramaS1002Chin DramaS1005Lee KarateS1001Smith KarateS1002Chin KarateS1005Lee StuNumberStuLastName S1001Smith S1002Chin S1005Lee ClubName Drama Karate

Set Operations Tables must be union compatible – A UNION B: A INTERSECTION B: A MINUS B:

SELECT Emp WHERE lastName = ‘Adams’ GIVING T1 JOIN T1, Assign GIVING T2 empIdprojNohours E101P10200 E101P15300 E105P10400 E110P15700 E110P20350 E115P10300 E115P20400 empIdlastName E101Smith E105Jones E110Adams E115Smith projNoprojNamebudget P10Hudson P15Columbia P20Wabash P23Arkansas600000

Example Tables STUDENT NAME AGE SEX Dole 21 M Carey 24 F Foley 28 F Mohler 31 M Wayson 18 F Beckman 23 F FACULTY NAME DEPT Gold HS Pierre FL Volmer PH Quincy FL Small BL Foley CS TRANS TNAME AGE SEX Claremont 23 F Diamon 20 M Jameson 21 F Adelman 19 M Mohler 31 M Gold 26 F

Sample Queries on the STUDENT/FACULTY/TRANS Database 1.Find the ages of all students 2.Find all information on males transferees 3. Find all 21 year olds who are students or transferees 4. Find the ages of all students who have the same name as a faculty member.

Sample Queries on the STUDENT/FACULTY/TRANS Database 5. Find all possible student advisor pairs. List their names only. 6. Find all transferees who are the same age as the student named Beckman. 7. Find all faculty in Quincy's department.