algebracalculus

# algebracalculus - The Relational Model - theoretical...

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Database Group, Georgia Tech © Leo Mark 1 Relational Model The Relational Model - theoretical foundation

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Database Group, Georgia Tech © Leo Mark 2 Relational Model The Relational Model data structures constraints operations algebra (ISBL) tuple calculus (QUEL, SQL) domain calculus (QBE) views
Database Group, Georgia Tech © Leo Mark 3 Relational Model Data Structures let D 1 , D 2 , D 3 , . .., D n be sets (not necessarily distinct) of atomic values relation, R , defined over D 1 , D 2 , D 3 , . .., D n is a subset of the set of ordered n- tuples {<d 1 , d 2 , d 3 , . .., d n | d i D i , i=1, . ..,n}; D 1 , D 2 , D 3 , . .., D n are called domains the number, n , is the degree of the relation (unary, binary, ternary, n-ary). the number of tuples, |R| , in R is called the cardinality of R if D 1 , D 2 , D 3 , . .., D n are finite then there are 2 | D1 | × | D2 | × ... × | Dn | possible relation states

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Database Group, Georgia Tech © Leo Mark 4 Relational Model Data Structures an attribute name refers to a position in a tuple by name rather than position an attribute name indicate the role of a domain in a relation attribute names must be unique within relations by using attribute names we can forget the ordering of field values in tuples a relation definition includes the following R( A 1 :D 1 , A 2 :D 2 , ..., A n :D n )
Database Group, Georgia Tech © Leo Mark 5 Relational Model Constraints keys primary keys entity integrity referential integrity RESERVATION FLT# DATE CUST# FLT-SCHEDULE FLT# CUSTOMER CUST# CUST-NAME p p

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Database Group, Georgia Tech © Leo Mark 6 Relational Model CUSTOMER cust# first middle last phone# street city state zip RESERVATION flt# date cust# seat# check-in-status ticket# AIRPORT airportcode name city state FLT-SCHEDULE flt# airline dtime from-airportcode atime to-airportcode miles price FLT-WEEKDAY flt# weekday AIRPLANE plane# plane-type total-#seats FLT-INSTANCE flt# date plane# #avail-seats
Database Group, Georgia Tech © Leo Mark 7 Relational Model Operations classes of relational DMLs: relational algebra (ISBL) tuple calculus (QUEL, SQL) domain calculus (QBE) a relational DML with the same “retrieval power” as the relational algebra is said to be relationally complete all relational DMLs have syntax for: change (insert, delete, update) queries (retrieval)

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Database Group, Georgia Tech © Leo Mark 8 Relational Model Operations - insert, delete, update constructs for insertion are very primitive: INSERT INTO FLT-SCHEDULE VALUES (“DL212”, “DELTA”, 11-15-00, “ATL”, 13-05-00, ”CHI”, 650, 00351.00); INSERT INTO FLT-SCHEDULE VALUES (FLT#:“DL212”, AIRLINE:“DELTA”); FLT-SCHEDULE flt# airline dtime from-airportcode atime to-airportcode miles price
Database Group, Georgia Tech © Leo Mark 9 Relational Model Operations - insert, delete, update insert into FLT-INSTANCE all flights

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## This note was uploaded on 01/12/2011 for the course MAT 1117 MAT 117 taught by Professor White during the Spring '09 term at University of Phoenix.

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algebracalculus - The Relational Model - theoretical...

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