B
A
BUNION
MINUS
INTERSECTION
Set Operations
UNION, INTERSECTION, MINUS
The next group of relational algebra operations are the standard mathematical operations on sets.
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Презентация на тему Analysis and Design of Data Systems. Relational Algebra 2 (Lecture 18)
Содержание
- 2. A
- 3. Set Operations UNION, INTERSECTION, MINUSUNION, INTERSECTION, and
- 4. UNIONExample: Retrieve the Social Security numbers of
- 5. Set operations (attributes naming)
- 6. CARTESIAN PRODUCT Operation (CROSS PRODUCT) Cartesian product operation
- 7. CARTESIAN PRODUCT Operation Example: retrieve a list
- 8. CARTESIAN PRODUCT Operation Step 2:Step 3:
- 9. CARTESIAN PRODUCT Operation Step 4:Step 5:Because this
- 10. Example: retrieve the name of the manager
- 11. where is of the form: AND AND … AND (condition)
- 12. Скачать презентацию
- 13. Похожие презентации
A BA BA BUNIONMINUSINTERSECTIONSet Operations UNION, INTERSECTION, MINUSThe next group of relational algebra operations are the standard mathematical
Слайд 2
A B
A
B
B
Слайд 3
Set Operations
UNION, INTERSECTION, MINUS
UNION, INTERSECTION, and MINUS are
binary operations.
This means that the two relations have the
same number of attributes and each corresponding pair of attributes has the same domain.
Слайд 4
UNION
Example: Retrieve the Social Security numbers of all
employees who either work in department 5 or directly
supervise an employee who works in department 5.Step 1:
Step 2:
Step 3:
Step 4:
or, as a single relational algebra expression:
Set operations eliminate duplicates
Слайд 6
CARTESIAN PRODUCT Operation
(CROSS PRODUCT)
Cartesian product operation produces a
new element by combining every tuple from one relation
with every tuple from the other relation.
The CARTESIAN PRODUCT operation by itself is generally meaningless, except when followed by a selection that matches values of attributes coming from the component relations.
Слайд 7
CARTESIAN PRODUCT Operation
Example: retrieve a list of names
of each female employee’s dependents
Step 1:
Step 2:
Step 3:
Step 4:
Step
5:Step 1:
Resulting Relations:
Слайд 9
CARTESIAN PRODUCT Operation
Step 4:
Step 5:
Because this sequence of
CARTESIAN PRODUCT followed by SELECT is quite commonly used to
combine related tuples from two relations, a special operation, called JOIN, was created to specify this sequence as a single operation.
Слайд 10
Example: retrieve the name of the manager of
each department.
SELECT d.Dname, e.Fname, e.Lname
FROM EMPLOYEE e, DEPARTMENT d
WHERE
Ssn = Mgr_ssn;
