Introduction to Database Systems Queries in SQL The select ...

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MotherChild mother child Lisa Mary Lisa Greg Anne Kim Anne Phil Mary Andy Mary Rob FatherChild father child Steve Frank Greg Kim Greg Phil Frank Andy Frank Rob Person name age Andy 27 Rob 25 Mary 55 Anne 50 Phil 26 Greg 50 Frank 60 Kim 30 Mike 85 Lisa 75 income 21 15 42 35 30 40 20 41 35 87 3 Selection and Projection Name and income of persons that are less than 30: π name, income (σ age
Naming Conventions • To avoid ambiguities, every attribute name has two components RelationName.AttributeName • When there is no ambiguity, one can drop the initial component RelationName. select person.name, person.income from person where person.age < 30 can be written as: select name, income from person where age < 30 5 select: Abbreviations select name, income from person where age < 30 is an abbreviation for: select person.name, person.income from person where person.age < 30 and also for: select p.name as name, p.income as income from person p where p.age < 30 6
Page 1: Introduction to Database Systems Qu
Page 5 and 6: Usage of “as” in select Stateme
Page 7 and 8: select with Asterisk Given a relati
Page 9 and 10: Handling of Null Values Employees w
Page 11 and 12: SQL and Relational Algebra Given th
Page 13 and 14: MotherChild mother child Lisa Mary
Page 15 and 16: Exercise 4: Solution “Father and
Page 17 and 18: Explicit Join For every person, ret
Page 19 and 20: A Further Extension: Natural Join (
Page 21 and 22: Ordering the Result: order by selec
Page 23 and 24: Results of count: Example FatherChi
Page 25 and 26: Aggregate Operators and the Target
Page 27 and 28: Exercise 7: group by “For each gr
Page 29 and 30: Conditions on Groups It is also pos
Page 31 and 32: Union, Intersection, and Difference
Page 33 and 34: Positional Notation (cntd) Renaming
Page 35 and 36: Single Block Queries: Exercises (cn
Page 37 and 38: Nested Queries: Example Name and in
Page 39 and 40: Nested Queries: Example with all
Page 41 and 42: Nested Queries and Negation All the
Page 43 and 44: Exercise 9: Solution with not exist
Page 45 and 46: More on Visibility Note: This query
Page 47 and 48: Exercise 10: Solution “Name and a
Page 49 and 50: Exercise 11 Can one express set dif
Page 51 and 52: Exercise 12: Solution “The person
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Solution with Views create view age
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Generic Integrity Constraints: chec
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Characteristics of Privileges A pri
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Example Transaction in SQL begin tr
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Transactions • A transaction is a
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Transactions are … Durable • Af
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Integrity Checking and Transactions
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Concurrency Control • There are t
Page 69 and 70:
Isolation Levels Prevent Violations
Page 71 and 72:
Transactions (Example ctd) Lubber a
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