Download Relational Database Manipulation Basic Relational Database Query

Basic Relational Database
Query Operations
• Three basic relational database query operations:
Relational Database
Manipulation
– Projection: retrieve selected attributes from a relation
– Selection (Restriction): retrieve selected tuples from a
relation
– Join: combine two or more relations
Robert C. Nickerson
ISYS 464 – Spring 2003
Topic 08
Copyright (c) 2003 by
Robert C. Nickerson
All rights reserved.
Not for general distribution.
• Note: All relational database query operations
take one or more relations as input and produce
one relation as output
1
Student
Student
N um ber
123
234
345
456
567
– Add: insert one or more new tuples in a relation
– Delete: remove one or more existing tuples from a
relation
– Change: modify certain data in one or more tuples of a
relation
C ourse
N um ber
ISY S 365
ISY S 464
ISY S 565
IB U S 330
FIN 350
M G M T 405
M K T G 431
3
• The operation of retrieving certain attributes from a relation
• Can project one or more attributes
• Example: Project the Student Name and Major attribute
from the Student relation
Output
Input
Copyright (c) 2003 by
Robert C. Nickerson
M ajor
IS
IS
Acct
M gmt
Acct
Student
Name
Joe
Fred
M ary
Sue
Lee
Student C ourse
M ajor
IS
IS
A cct
M gm t
A cct
C ourse N am e
D ay
T im e
A dv C ++
D atabase
D ata C om m
Int B usiness
Finance
O rg B ehavior
M arketing
MW
T Th
T Th
MW
MW
MW
T Th
12:30
9:30
14:00
8:00
14:00
15:30
8:00
Copyright (c) 2003 by
Robert C. Nickerson
Student
N um ber
123
123
123
234
234
234
234
345
567
567
567
678
678
C ourse
N um ber
ISY S 365
FIN 350
M G M T 405
ISY S 365
FIN 350
M G M T 405
M K T G 431
ISY S 464
ISY S 464
ISY S 565
M G M T 405
ISY S 363
M G M T 405
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Not for general distribution.
4
Selection (Restriction)
Projection
Student
Name
Joe
Fred
M ary
Sue
Lee
Student
N am e
Joe
Fred
M ary
Sue
L ee
C ourse
• Note: All relational database update operations
take one relation as input and produce a modified
form of that relation as output
Student
Student
Number
123
234
345
456
567
2
Student (Student Number, Student Name, Major)
Course (Course Number, Course Name, Day, Time)
Student Course (Student Number, Course Number)
• Three basic relational database update operations:
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Not for general distribution.
Student Course Database
Basic Relational Database
Update Operations
Copyright (c) 2003 by
Robert C. Nickerson
Copyright (c) 2003 by
Robert C. Nickerson
IS
IS
Acct
M gmt
Acct
Copyright (c) 2003 by Robert C. Nickerson.
All rights reserved. Not for general
distribution.
Output
Input
Course
Course
Number
ISYS 365
ISYS 464
ISYS 565
IBUS 330
FIN 350
MGMT 405
MKTG 431
M ajor
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Not for general distribution.
• The operation of retrieving certain tuples from a relation
based on a condition
• Selection can result in one or more tuples, or no tuples if no
tuples in the relation satisfy the condition
• Example: Select all tuples from the Course relation where
the course is taught on TTh
5
Course Name Day
Adv C++
Database
Data Comm
Int Business
Finance
Org Behavior
Marketing
Copyright (c) 2003 by
Robert C. Nickerson
MW
TTh
TTh
MW
MW
MW
TTh
Time
12:30
9:30
14:00
8:00
14:00
15:30
8:00
Course
Number
ISYS 464
ISYS 565
MKTG 431
All rights reserved.
Not for general distribution.
Course Name Day
Time
Database
Data Comm
Marketing
9:30
14:00
8:00
TTh
TTh
TTh
6
1
Example: Join
Join
Input
Student
Student
Number
123
234
345
456
567
• The operation of combining the tuples of
two relations based on a condition
• Example: Join the Student relation and the
Student Course relation based on the
Student Number in the Student relation
equaling the Student Number in the Student
Course relation
Copyright (c) 2003 by
Robert C. Nickerson
All rights reserved.
Not for general distribution.
7
M ajo r
IS
IS
IS
IS
IS
IS
IS
A cct
A cct
A cct
A cct
S tud en t
N u m ber
123
123
123
234
234
234
234
345
567
567
567
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Not for general distribution.
– One-to-one: Each tuple of one relation will match zero or one
tuples of the other relation
– One-to-many: Each tuple of the parent relation will match zero,
one, or more tuples of the child relation
– Many-to-many: Requires joining three relations, the two related
relations and the intersection relation. Each tuple of one related
relation is matched with related tuples in the other related relation,
and vice versa, through the intersection relation.
• Note: Join can result in no tuples if condition is not met
9
Join Terminology
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Copyright (c) 2003 by Robert C. Nickerson.
All rights reserved. Not for general
distribution.
8
• Join with different relationships:
• Join condition: the condition that indicates under what
circumstances tuples in the two relations are to be combined
• Note: We can have a join involving any of the relational
operators: =, <>, >, >=, <, <=
• Equijoin: a join involving an equal join condition
• Note: Only with an equijoin are we guaranteed to have two
attributes that are identical in the result of the join
• Natural join: an equijoin in which one of the duplicate
attributes is automatically eliminated
Copyright (c) 2003 by
Robert C. Nickerson
All rights reserved.
Not for general distribution.
– By joining two relations based on the primary key of one relation
equaling the corresponding foreign key of another relation, we
match related tuples from the two relations
C o u rse
N u m b er
IS Y S 3 6 5
F IN 3 5 0
M G M T 405
IS Y S 3 6 5
F IN 3 5 0
M G M T 405
M K T G 43 1
IS Y S 4 6 4
IS Y S 4 6 4
IS Y S 5 6 5
M G M T 405
Unmatched Student tuples and unmatched Student
Course tuples do not appear in the output.
Copyright (c) 2003 by
Robert C. Nickerson
IS
IS
Acct
M gm t
Acct
Student Course
Student
Course
Number
Number
123
ISYS 365
123
FIN 350
123
M GM T 405
234
ISYS 365
234
FIN 350
234
M GM T 405
234
M KTG 431
345
ISYS 464
567
ISYS 464
567
ISYS 565
567
M GM T 405
678
ISYS 363
678
M GM T 405
• Join is the operation we use to utilize relationships in
relational databases:
O u tp u t
S tud en t
N am e
Jo e
Jo e
Jo e
F red
F red
F red
F red
M ary
L ee
L ee
L ee
Copyright (c) 2003 by
Robert C. Nickerson
M ajor
Join Use
Example: Join
S tud en t
N u m b er
123
123
123
234
234
234
234
345
567
567
567
Student
Name
Joe
Fred
M ary
Sue
Lee
11
Copyright (c) 2003 by
Robert C. Nickerson
All rights reserved.
Not for general distribution.
10
Inner and Outer Joins
• Inner join: a join in which tuples in the two joined relations
that do not satisfy the join condition are not included in the
result
• Note: An inner join is assumed unless otherwise stated
• Example: Previous example was an inner join
• Outer join (full outer join): a join in which tuples in the
two joined relations that do not satisfy the join condition are
included in the result
• Example: Outer join of Student and Student Course
relations based on the Student Number in the Student
relation equaling the Student Number in the Student Course
relation
Copyright (c) 2003 by
Robert C. Nickerson
All rights reserved.
Not for general distribution.
12
2
Example: Outer Join
Left and Right Outer Join
O u tp u t
S tu d e n t
N um ber
123
123
123
234
234
234
234
345
456
567
567
567
NULL
NULL
S tu d e n t
N am e
Jo e
Jo e
Jo e
F re d
F re d
F re d
F re d
M ary
Sue
L ee
L ee
L ee
NULL
NULL
M a jo r
IS
IS
IS
IS
IS
IS
IS
A cct
M gm t
A cct
A cct
A cct
NULL
NULL
S tu d e n t
N um ber
123
123
123
234
234
234
234
345
NULL
567
567
567
678
678
C o u rs e
N um ber
IS Y S 3 6 5
F IN 3 5 0
M G M T 405
IS Y S 3 6 5
F IN 3 5 0
M G M T 405
M K TG 431
IS Y S 4 6 4
NULL
IS Y S 4 6 4
IS Y S 5 6 5
M G M T 405
IS Y S 3 6 3
M G M T 405
• Left outer join: a join in which tuples in the relation
named first (on the left) that do not satisfy the join
condition are included in the result
• Right outer join: a join in which tuples in the
relation named second (on the right) that do not
satisfy the join condition are included in the result
Note NULLs for attributes of unmatched tuples
Copyright (c) 2003 by
Robert C. Nickerson
All rights reserved.
Not for general distribution.
13
Copyright (c) 2003 by
Robert C. Nickerson
All rights reserved.
Not for general distribution.
Example: Right Outer Join
Example: Left Outer Join
• Example: Left outer join of Student and Student Course relations
based on the Student Number in the Student relation equaling the
Student Number in the Student Course relation
• Example: Right outer join of Student and Student Course relations
based on the Student Number in the Student relation equaling the
Student Number in the Student Course relation
O u tp u t
O u tp u t
S tud en t
N u m b er
123
123
123
234
234
234
234
345
456
567
567
567
Copyright (c) 2003 by
Robert C. Nickerson
S tud en t
N am e
Jo e
Jo e
Jo e
F red
F red
F red
F red
M ary
Sue
L ee
L ee
L ee
M ajo r
IS
IS
IS
IS
IS
IS
IS
A cct
M gm t
A cct
A cct
A cct
S tud en t
N u m ber
123
123
123
234
234
234
234
345
NULL
567
567
567
C o u rse
N u m b er
IS Y S 3 6 5
F IN 3 5 0
M G M T 405
IS Y S 3 6 5
F IN 3 5 0
M G M T 405
M K T G 43 1
IS Y S 4 6 4
NULL
IS Y S 4 6 4
IS Y S 5 6 5
M G M T 405
All rights reserved.
Not for general distribution.
S tu d e n t
N um ber
123
123
123
234
234
234
234
345
567
567
567
NULL
NULL
15
Relational Database Languages
– Data Manipulation Language (DML) – used to
query and update the data in a database
– Data Definition Language (DDL) – used to
define the characteristics of a database
– Data Control Language (DCL) – used to control
user access to a database
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Not for general distribution.
Copyright (c) 2003 by Robert C. Nickerson.
All rights reserved. Not for general
distribution.
Copyright (c) 2003 by
Robert C. Nickerson
S tu d e n t
N am e
Jo e
Jo e
Jo e
F re d
F re d
F re d
F re d
M a ry
L ee
L ee
L ee
NULL
NULL
M a jo r
IS
IS
IS
IS
IS
IS
IS
A cct
A cct
A cct
A cct
NULL
NULL
S tu d e n t
N um ber
123
123
123
234
234
234
234
345
567
567
567
678
678
C o u rse
N um ber
IS Y S 3 6 5
F IN 3 5 0
M G M T 405
IS Y S 3 6 5
F IN 3 5 0
M G M T 405
M K TG 431
IS Y S 4 6 4
IS Y S 4 6 4
IS Y S 5 6 5
M G M T 405
IS Y S 3 6 3
M G M T 405
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Not for general distribution.
16
Data Manipulation Language (DML)
• Three main sub-languages in a relational
database language
Copyright (c) 2003 by
Robert C. Nickerson
14
17
• A language used to query and update the
data in a database
• A relational database is manipulated by a
relational DML
• Two main types of relational DMLs:
– Relational algebra
– Relational calculus
Copyright (c) 2003 by
Robert C. Nickerson
All rights reserved.
Not for general distribution.
18
3
Relational Calculus
Relational Algebra
• Procedural (like algebra: x2 + 2x + 3 )
• States how to obtain result by giving the sequence of
operations
• Example using hypothetical relational algebra: What are
the names of all students taking ISYS 263?
•
•
•
•
Non-procedural (like calculus: ∫ x2 dx )
States what is wanted, not how to obtain it
Query by Example (QBE) is a type of relational calculus
Example using QBE: What are the names of all students taking ISYS
263?
Order of processing is
not given
Student_Course WHERE Course_Number = 'ISYS 263' JOIN
(Student_Course.Student_Number = Student.Student_Number)
Student [Student_Name]
Order determined by
software
• Processing performed left to right through the command
Copyright (c) 2003 by
Robert C. Nickerson
All rights reserved.
Not for general distribution.
19
Hybrid Relational DML
• Combines elements of relational algebra and relational
calculus
• Some procedural and some non-procedural characteristics
• States what is wanted but may state some sequencing of
operations
• Example using SQL: What are the names of all students
taking ISYS 263?
SELECT Student_Name
FROM Student, Student_Course
WHERE Student.Student_Number = Student_Course.Student_Number
AND Course_Number = 'ISYS 263‘
• SQL is sometimes called a transform-oriented language
Copyright (c) 2003 by
Robert C. Nickerson
All rights reserved.
Not for general distribution.
21
QBE is sometimes
called a graphical
language
Copyright (c) 2003 by
Robert C. Nickerson
All rights reserved.
Not for general distribution.
20
Data Definition Language (DDL)
• A language used to define the characteristics
of a database
• DDL permits:
– Definition of relations in the conceptual view of
the database
– Definition of relations in each external view of
the database
– Definition of structures used to enhance
performance (e.g., indexes)
Copyright (c) 2003 by
Robert C. Nickerson
All rights reserved.
Not for general distribution.
22
Data Control Language (DCL)
• A language used to control user access to
the database
• DCL permits:
– Giving of privileges to users (e.g., access,
update privileges)
– Removing privileges from users
Copyright (c) 2003 by
Robert C. Nickerson
All rights reserved.
Not for general distribution.
Copyright (c) 2003 by Robert C. Nickerson.
All rights reserved. Not for general
distribution.
23
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