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Carnegie Mellon Univ. Dept. of Computer Science 15-415 - Database Applications. C. Faloutsos Relational domain calculus. General Overview. relational model Formal query languages relational algebra rel. tuple calculus rel. domain calculus. Overview - detailed. rel. tuple calculus dfn

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carnegie mellon univ dept of computer science 15 415 database applications

Carnegie Mellon Univ.Dept. of Computer Science15-415 - Database Applications

C. Faloutsos

Relational domain calculus

general overview
General Overview
  • relational model
  • Formal query languages
    • relational algebra
    • rel. tuple calculus
    • rel. domain calculus

15-415 - C. Faloutsos

overview detailed
Overview - detailed
  • rel. tuple calculus
    • dfn
    • details
    • equivalence to rel. algebra
  • rel. domain calculus + QBE

15-415 - C. Faloutsos

rel domain calculus rdc
Rel. domain calculus (RDC)
  • Q: why?
  • A: slightly easier than RTC, although equivalent - basis for QBE.
  • idea: domain variables (w/ F.O.L.) - eg:
  • ‘find STUDENT record with ssn=123’

15-415 - C. Faloutsos

rel dom calculus
Rel. Dom. Calculus
  • find STUDENT record with ssn=123’

15-415 - C. Faloutsos

details
Details
  • Like R.T.C - symbols allowed:
  • quantifiers

15-415 - C. Faloutsos

details1
Details
  • but: domain (= column) variables, as opposed to tuple variables, eg:

ssn

address

name

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reminder our mini u db
Reminder: our Mini-U db

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examples
Examples
  • find all student records

RTC:

15-415 - C. Faloutsos

examples1
Examples
  • (selection) find student record with ssn=123

15-415 - C. Faloutsos

examples2
Examples
  • (selection) find student record with ssn=123

or

RTC:

15-415 - C. Faloutsos

examples3
Examples
  • (projection) find name of student with ssn=123

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examples4
Examples
  • (projection) find name of student with ssn=123

need to ‘restrict’ “a”

RTC:

15-415 - C. Faloutsos

examples cont d
Examples cont’d
  • (union) get records of both PT and FT students

RTC:

15-415 - C. Faloutsos

examples cont d1
Examples cont’d
  • (union) get records of both PT and FT students

15-415 - C. Faloutsos

examples5
Examples
  • difference: find students that are not staff

RTC:

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examples6
Examples
  • difference: find students that are not staff

15-415 - C. Faloutsos

cartesian product
Cartesian product
  • eg., dog-breeding: MALE x FEMALE
  • gives all possible couples

=

x

15-415 - C. Faloutsos

cartesian product1
Cartesian product
  • find all the pairs of (male, female) - RTC:

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cartesian product2
Cartesian product
  • find all the pairs of (male, female) - RDC:

15-415 - C. Faloutsos

proof of equivalence
‘Proof’ of equivalence
  • rel. algebra <-> rel. domain calculus

<-> rel. tuple calculus

15-415 - C. Faloutsos

overview detailed1
Overview - detailed
  • rel. domain calculus
    • why?
    • details
    • examples
    • equivalence with rel. algebra
    • more examples; ‘safety’ of expressions

15-415 - C. Faloutsos

more examples
More examples
  • join: find names of students taking 15-415

15-415 - C. Faloutsos

reminder our mini u db1
Reminder: our Mini-U db

15-415 - C. Faloutsos

more examples1
More examples
  • join: find names of students taking 15-415 - in RTC

15-415 - C. Faloutsos

more examples2
More examples
  • join: find names of students taking 15-415 - in RDC

15-415 - C. Faloutsos

sneak preview of qbe
Sneak preview of QBE:

15-415 - C. Faloutsos

sneak preview of qbe1
Sneak preview of QBE:
  • very user friendly
  • heavily based on RDC
  • very similar to MS Access interface

15-415 - C. Faloutsos

more examples3
More examples
  • 3-way join: find names of students taking a 2-unit course - in RTC:

join

projection

selection

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reminder our mini u db2
Reminder: our Mini-U db

_x

.P

_y

2

_x

_y

15-415 - C. Faloutsos

more examples4
More examples
  • 3-way join: find names of students taking a 2-unit course

15-415 - C. Faloutsos

more examples5
More examples
  • 3-way join: find names of students taking a 2-unit course

15-415 - C. Faloutsos

even more examples
Even more examples:
  • self -joins: find Tom’s grandparent(s)

15-415 - C. Faloutsos

even more examples1
Even more examples:
  • self -joins: find Tom’s grandparent(s)

15-415 - C. Faloutsos

even more examples2
Even more examples:
  • self -joins: find Tom’s grandparent(s)

15-415 - C. Faloutsos

even more examples3
Even more examples:
  • self -joins: find Tom’s grandparent(s)

15-415 - C. Faloutsos

hard examples division
Hard examples: DIVISION
  • find suppliers that shipped all the ABOMB parts

15-415 - C. Faloutsos

hard examples division1
Hard examples: DIVISION
  • find suppliers that shipped all the ABOMB parts

15-415 - C. Faloutsos

hard examples division2
Hard examples: DIVISION
  • find suppliers that shipped all the ABOMB parts

15-415 - C. Faloutsos

more on division
More on division
  • find students that take all the courses that ssn=123 does (and maybe even more)

15-415 - C. Faloutsos

more on division1
More on division
  • find students that take all the courses that ssn=123 does (and maybe even more)

15-415 - C. Faloutsos

safety of expressions
Safety of expressions
  • similar to RTC
  • FORBIDDEN:

15-415 - C. Faloutsos

overview detailed2
Overview - detailed
  • rel. domain calculus + QBE
    • dfn
    • details
    • equivalence to rel. algebra

15-415 - C. Faloutsos

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