Relational Model Introduction - E-Courses

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Join Operation • Cross product : produces all combinations of tuples • often only certain combinations are meaningful • cross product is usually followed by selection • Join : combines tuples from two relations provided they satisfy a specified condition (join condition) • equivalent to performing cross product followed by selection • a very useful operation • Depending on the type of condition we have • theta join • equi join Prof P Sreenivasa Kumar Department of CS&E, IITM 28
Theta join • Let r 1 - relation with scheme R 1 = (A 1 ,A 2 ,…,A m ) r 2 - relation with scheme R 2 = (B 1 ,B 2 ,…,B n ) and R 1 ∩ R 2 = φ • Notation for join expression : r 1 ⋈ θ r 2 , θ - join condition θ is of the form : C 1 ^ C 2 ^ … ^ C s C i is of the form : A j B k : = , ≠, < , ≤ , > , ≥ • Scheme of the result relation Q = (A 1 ,A 2 ,…,A m ,B 1 ,B 2 ,…,B n ) • r = {(a1 ,a2 ,…,am ,b1 ,b2 ,…,bn ) (a1 ,a2 ,…,am ) ∈ r1 , (b 1 ,b 2 ,…,b n ) r 2 and (a 1 ,a 2 ,…,a m ,b 1 ,b 2 ,…,b n ) satisfies θ} ∈ Prof P Sreenivasa Kumar Department of CS&E, IITM 29
Page 1 and 2: Introduction Relational Model Prop
Page 3 and 4: Relation Instance A finite set of
Page 5 and 6: Keys for a Relation (2/2) A relati
Page 7 and 8: Domain and Key Constraints • Doma
Page 9 and 10: Foreign Key - Examples(1/2) Foreign
Page 11 and 12: Referential Integrity Constraint (R
Page 13 and 14: Example Relational Scheme student (
Page 15 and 16: Example Relational Scheme student (
Page 17 and 18: Relational Algebra A set of operat
Page 19 and 20: Selection Condition • Select cond
Page 21 and 22: The project Operator Unary operato
Page 23 and 24: Size of project expression result
Page 25 and 26: Set Operations r 1 - relation with
Page 27: Example Query using cross product
Page 31 and 32: Examples For each department, find
Page 33 and 34: Examples - Equi-join Find courses o
Page 35 and 36: Division operator The necessary co
Page 37 and 38: Query using division operation Find
Page 39 and 40: Complete Set of Operators • Are a
Page 41 and 42: More Example Queries Obtain the dep
Page 43 and 44: Outer Join Operation (2/2) Left out
Page 45 and 46: Left outer join temp ← (student a
Page 47 and 48: Full outer join temp ← (student a
Page 49 and 50: Relational representation of strong
Page 51 and 52: Example CourseID Name Credits Corre
Page 53 and 54: Handling Binary 1:1 relationship L
Page 55 and 56: Handling 1:N Relationship Let S be
Page 57 and 58: Handling M:N relationship Make a s
Page 59: Handling Recursive relationships M

Relational Model Introduction - E-Courses

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