1. Chapter 13 Views (up to p.495) Jason C. H. Chen, Ph.D.
Professor of MIS
School of Business
Gonzaga University
Spokane, WA USA

2. Objectives
Create a view by using CREATE VIEW command or the CREATE OR REPLACE VIEW command
Employ the FORCE and NOFORCE options
State the purpose of the WITH CHECK OPTION constraint
Explain the effect of the WITH READ ONLY option
Update a record in a simple view
Re-create a view

3. Objectives (continued)
Explain the implication of an expression in a view for DML operations
Update a record in a complex view
Identify problems associated with adding records to a complex view
Identify the key-preserved table underlying a complex view
Drop a view
Explain inline views and the use of ROWNUM to perform a “TOP-N” analysis
Create a materialized view to replicate data

4. Database Views Table-1 Table-2 Table-N database Database view Query
A database view is a logical (virtual) table based on a query.
Table-1
Table-2
Table-N
It does not store data, but presents it in a format different from the one in which it is stored in the underlying tables.
With the database view, you can view database records, but you can’t insert new records or modify or delete exiting records.
database
Single view table
Database view
Query
Output:
Report, Graphs

5. Views
Permanent objects (logical or virtual table) that store queries but ____ data
Based on a source query that:
can specify a subset of a single table’s fields or records
can join multiple tables
Two purposes
Reduce complex query requirements
Restrict users’ access to sensitive data (enforce security; user has access to view but not underlying table) no

6. Creating and Using Database Views
Views can be updateable if:
SELECT clause contains only fieldnames, no functions or calculations
Can ____ contain the ORDER BY, DISTINCT, or GROUP BY clauses, group functions, or set operators
search condition cannot contain a nested query
Views are used like tables for selecting, inserting, updating and deleting data (only updatable views can be modified)
not

7. Database View (cont.) SELECT view_name FROM user_views;
SELECT view_name FROM ALL_VIEWS
WHERE owner=‘SYSTEM’;
DROP VIEW <view_name>;
CREATE OR REPLACE VIEW <view_name> AS
<view query specification>;

8. Types of Views
Table Overview of View Concepts

9. I. Creating a View You use the CREATE VIEW keywords to create a view
Use OR REPLACE if the view already exists
Use FORCE if the underlying table does not exist at the time of creation
Provide new column names if necessary
WITH CHECK OPTION constraint – if used, prevents data changes that will make the data subsequently inaccessible to the view
WITH READ ONLY – prevents DML operations
Figure Syntax of the CREATE VIEW command

10. CREATE OR REPLACE VIEW book_vu AS SELECT isbn, title, category
FROM books
WHERE category = 'COOKING';
SELECT *
FROM book_vu;
SQL> SELECT *
2 FROM book_vu;
ISBN TITLE CATEGORY
COOKING WITH MUSHROOMS COOKING
THE WOK WAY TO COOK COOKING
See next slide for detailed process

11. FROM clause in query references a view rather than a table
BOOK_VU view
(view stored in database)
SELECT*
FROM book_vu;
Stores query:
SELECT isbn, title, category
FROM books
WHERE category=‘COOKING’; 1 3 4 2
Processing steps:
A query references a view rather than a table in the FROM clause.
The query stored in the view is executed.
The results from the view query are stored in temporary storage.
The original query uses the temporary query results of the view as a table and completes execution.
Figure View Processing

12. DML Operations on a Simple View
Any DML operations are allowed through simple views unless created with WITH READ ONLY option
DML operations that violate constraints on the underlying table are not allowed
-- chapter 13, Figure 13-5; p.478
CREATE VIEW region_ne
AS SELECT *
FROM customers
WHERE region = 'NE';
SELECT customer#, lastname, city, state, region
FROM region_ne;
-- chapter 13, Figure 13-4; p.477
CREATE VIEW inventory
AS SELECT isbn, title, retail price
FROM books
WITH READ ONLY;
SELECT *
FROM inventory;

13. Why Failed to Update? -- chapter 13, Figure 13-6; p.479
UPDATE inventory
SET price = 45.96
WHERE title LIKE '%POEM';
-- “SELECT” is working (READ)
SELECT *
FROM inventory
WHERE title LIKE '%POEM%';
SET title = 'THE SHORTEST POEMS'
SQL> UPDATE inventory
2 SET price = 45.96
3 WHERE title LIKE '%POEM';
SET price = 45.96 *
ERROR at line 2:
ORA-42399: cannot perform a DML operation on a read-only view
ISBN TITLE PRICE
SHORTEST POEMS
SQL> UPDATE inventory
2 SET title = 'THE SHORTEST POEMS'
3 WHERE title LIKE '%POEM%';
SET title = 'THE SHORTEST POEMS' *
ERROR at line 2:
ORA-42399: cannot perform a DML operation on a read-only view
READY ONLY
Figure Failed updates on the INVENTORY view

14. Combining Topics – VIEW and NON-Equality Join
Combing both VIEW (chapter 13) and NON-EQUALITY JOINS (chapter 9; p.304)
A non-equality join enables you to store a range's minimum value in one column of a record and the maximum value in another column. So instead of finding a column-to-column match, you can use a non-equality join to determine whether the item being shipped falls between minimum and maximum ranges in the columns.
If the join does find a matching range for the item, the corresponding shipping fee (and others) can be returned in the results

15. Business Scenario
Once a year, JustLee Books offers weeklong promotion in which customers receive a gift based on the value of each book purchase. If a customer purchases a book with a retail price of $12 or less, the customer receives a bookmark. If the retail price is more than $12 but less than or equal to $25, the customer receives a box of book-owner labels.
For books retailing for more than $25 and less than or equal to $56, the customer is entitled to a free book cover. For books retailing for more than $56, the customer receives free shipping.
SQL> SELECT * FROM promotion;
GIFT MINRETAIL MAXRETAIL
BOOKMARKER
BOOK LABELS
BOOK COVER
FREE SHIPPING

16. Task …
Your job is to produce a report listing book title, publisher name, profit and its gift (note individual gift that is based on the retail price falls between minimal and maximal retail prices)
Hint:
Because the rows in the BOOKS and PROMOTION tables don't contain equivalent values (pk and fk), you must use a non-equality join to determine which gift a customer receives during the promotion.

17. -- First Create VIEW for ‘book’ and publisher
CREATE OR REPLACE VIEW book_profit_vu AS
SELECT b.title, pu.name Publisher_Name, b.retail, b.retail-b.cost Profit
FROM books b, publisher pu
WHERE b.pubid = pu.pubid;
SQL> SELECT * FROM book_profit_vu;
TITLE PUBLISHER_NAME RETAIL PROFIT
REVENGE OF MICKEY PRINTING IS US
HOW TO MANAGE THE MANAGER PRINTING IS US
E-BUSINESS THE EASY WAY PUBLISH OUR WAY
BUILDING A CAR WITH TOOTHPICKS PUBLISH OUR WAY
HOLY GRAIL OF ORACLE AMERICAN PUBLISHING
DATABASE IMPLEMENTATION AMERICAN PUBLISHING
HANDCRANKED COMPUTERS AMERICAN PUBLISHING
COOKING WITH MUSHROOMS READING MATERIALS INC
THE WOK WAY TO COOK READING MATERIALS INC
HOW TO GET FASTER PIZZA READING MATERIALS INC
BODYBUILD IN 10 MINUTES A DAY READING MATERIALS INC
PAINLESS CHILD-REARING REED-N-RITE
BIG BEAR AND LITTLE DOVE REED-N-RITE
SHORTEST POEMS REED-N-RITE
14 rows selected.

18. -- use "NON-EQUALITY JOIN" (p.304)
SELECT title, Publisher_name, retail, p.gift, TO_CHAR(profit, '$999.99') Proft
FROM book_profit_vu bpvu, promotion p
WHERE bpvu.retail BETWEEN p.minretail AND p.maxretail
ORDER BY profit;
column title format A23
COLUMN name format A18
column proft format $999.99
column retail format $999.99
column gift format A13
SELECT title, Publisher_name, retail, p.gift, TO_CHAR(profit, '$999.99') Proft
FROM book_profit_vu bpvu, promotion p
WHERE bpvu.retail BETWEEN p.minretail AND p.maxretail
ORDER BY profit;

19. TITLE PUBLISHER_NAME RETAIL GIFT PROFT
HANDCRANKED COMPUTERS AMERICAN PUBLISHING $25.00 BOOK LABELS $3.20
BIG BEAR AND LITTLE DOV REED-N-RITE $8.95 BOOKMARKER $3.63 E
COOKING WITH MUSHROOMS READING MATERIALS INC. $19.95 BOOK LABELS $7.45
REVENGE OF MICKEY PRINTING IS US $22.00 BOOK LABELS $7.80
THE WOK WAY TO COOK READING MATERIALS INC. $28.75 BOOK COVER $9.75
HOW TO GET FASTER PIZZA READING MATERIALS INC. $29.95 BOOK COVER $12.10
BODYBUILD IN 10 MINUTES READING MATERIALS INC. $30.95 BOOK COVER $12.20
A DAY
HOW TO MANAGE THE MANAG PRINTING IS US $31.95 BOOK COVER $16.55 ER
E-BUSINESS THE EASY WAY PUBLISH OUR WAY $54.50 BOOK COVER $16.60
SHORTEST POEMS REED-N-RITE $39.95 BOOK COVER $18.10
BUILDING A CAR WITH TOO PUBLISH OUR WAY $59.95 FREE SHIPPING $22.15
THPICKS
DATABASE IMPLEMENTATION AMERICAN PUBLISHING $55.95 BOOK COVER $24.55
HOLY GRAIL OF ORACLE AMERICAN PUBLISHING $75.95 FREE SHIPPING $28.70
PAINLESS CHILD-REARING REED-N-RITE $89.95 FREE SHIPPING $41.95
14 rows selected.
GIFT MINRETAIL MAXRETAIL
BOOKMARKER
BOOK LABELS
BOOK COVER
FREE SHIPPING

20. A Version without VIEW
--1c.(TRADITIONAL JOIN; modified version from p.305)
SELECT b.title, pu.name "Publisher Name", b.retail, p.gift, b.retail-b.cost proft
FROM books b, publisher pu, promotion p
WHERE b.pubid = pu.pubid
AND b.retail BETWEEN p.minretail AND p.maxretail
ORDER BY b.retail-b.cost;

21. DML Operations on a Simple View (continued)
-- chapter 13, Figure 13-7; p.480
CREATE OR REPLACE VIEW inventory
AS SELECT isbn, title, retail price
FROM books;
SELECT *
FROM inventory
WHERE title LIKE '%BODYBUILD%';
-- chapter 13, Figure 13-8; p.481
UPDATE inventory
SET price = 49.95
WHERE title LIKE '%BODYBUILD%';
SELECT *
FROM inventory
FROM books

22. Rule for DML operations
As long as the view isn’t created with the WITH READ ONLY option and any DML operation is allowed if it doesn’t violate an existing constraint on the underlying table.
You can add, modify, and even delete data in an underlying table as long as one of the following constraints doesn’t prevent the operation:
PRIMARY KEY - FOREIGN KEY
UNIQUE NOT NULL
WITH CHECK OPTION
Practice Figure 13-9 to (pp )

23. Practice all the examples in the text.
Exercises
Practice all the examples in the text.
A Script file is available on the Bb (file name: ch13Queries.sql)
After completing all examples, do the HW.
In-class Exercise #1
--1.
CREATE VIEW contact
AS SELECT contact, phone
FROM publisher;

24. Homework - Hands-On Assignments
me with one attachment
(Oracle_ch13_Spool_Lname_Fname.) to:
with subject title of
bmis441_Oracle_ch13 (or Bmis441-02_Oracle_ch13)
Read and Practice all examples on Chapters 13
1. Read Oracle assignment and create a script file Oracle_ch13_Lname_Fname.sql for questions (#1-5 and 9,10; p.508) on “Hands-on Assignments”.
2. Execute and test one problem at a time and make sure they are all running successfully.
3. When you done, spool the script files (see next slide for spooling instructions) and UPLOAD script and spooled files (Oracle_ch13_Spool_Lname_Fname.txt) by the midnight before the next class.

25. How to Spool your Script and Output Files
After you tested the script file of Oracle_ch13_Lname_Fname.sql successfully, follow the instructions below to spool both script and output files:
Step 0. Run the following script file from SQL*Plus (since you have created JLDB tables)
1. type the following on SQL>
Spool c:\oradata\Oracle_ch13B_Spool_Lname_Fname.txt (make sure your name is entered)
2. open Oracle_ch13_Lname_Fname.sql that you already tested
3. copy and paste all the SQL commands (including all comments) to the SQL*PLUS
4. type Spool Off on the SQL>
The output should contain your personal information, all SQL commands and their solution on the .txt file and saved in C: drive (oradata\ folder)
UPLOAD script and spooled files (*.sql and *.txt)

26. PART II

27. II. Creating a Complex View
A complex view may contain data from multiple tables or data created with the GROUP BY clause, functions, or expressions
Type of DML operations allowed depends on various factors

28. DML Operations on a Complex View with an Arithmetic Expression
Figure Create and update a complex view named prices

29. Rule#1: DML operations are not permitted if the view includes a column based on arithmetic expression
Figure Failed attempts to add a new book via the PRICES view
-- chapter 13, Figure 13-15; p.488
INSERT INTO prices (isbn, title, cost, retail)
VALUES( , 'A New Book', 8.95, 15.95);

30. Rule#2: DML operations are not permitted if they violate a constraint such as NOT NULL, UNIQUE etc.
no pubid is inserted
Figure Constraint violation with an INSERT command via the PRICES view

31. DML Operations on a Complex View Containing Data from Multiple Tables
DML operations cannot be performed on non-key-preserved tables, but they are permitted on key-preserved tables
Figure PRICES view with a table join
Practice: Figure 13-18

32. DML Operations on a Complex View Containing Data from Multiple Tables (continued)
Rule#3: DML operations can’t be performed on a non-key-preserved table.
Figure Failed attempt to update the publisher name via the PRICES view

33. DML Operations on a Complex View Containing Functions or Grouped Data
Rule#4: DML operations are not permitted if the view includes a group function or a GROUP BY clause, the DISTINCT keyword, or the ROWNUM pseudocolumn.
-- chapter 13, Figure 13-21; p.492
CREATE VIEW balancedue
AS SELECT customer#, order#, SUM(quantity * retail) Amtdue
FROM customers JOIN orders USING (customer#)
JOIN orderitems USING (order#)
JOIN books USING (isbn)
GROUP BY customer#, order#;
SELECT *
FROM balancedue;
Figure View including grouped data

34. SELECT *
FROM balancedue;
Figure View including grouped data

35. DML Operations on a Complex View Containing Functions or Grouped Data (continued)
Figure Failed DELETE command on a view with grouped data

36. Dropping a View Use DROP VIEW command
Figure Command to drop the PRICES view

37. III. Creating an Inline View
An inline view is a temporary table created by using a subquery in the FROM clause
It can only be referenced while the command is being executed
Most common usage – “TOP-N” analysis

38. ORDER BY included to identify top values:
“TOP-N” Analysis
ORDER BY included to identify top values:
Descending for highest values
Ascending for lowest values
Extract data based on ROWNUM
Up to “N” rows returned
Figure Syntax of TOP-N analysis

39. “TOP-N” Analysis (continued)
Figure TOP-N analysis to identify the five most profitable books

40. Figure 13-28 TOP-N analysis to identify the five most profitable books
Figure TOP-N analysis to determine the three lest profitable books

41. Practice all the examples in the text.
Exercises
Practice all the examples in the text.
A Script file is available on the Bb (file name: ch13Queries.sql)
After completing all examples, do the HW.
In-class Exercise #1
--1.
CREATE VIEW contact
AS SELECT contact, phone
FROM publisher;

42. Homework - Hands-On Assignments
me with one attachment
(Oracle_ch13_Spool_Lname_Fname.) to:
with subject title of
Bmis441-01_Oracle_ch13 (or Bmis441-02_Oracle_ch13)
Read and Practice all examples on Chapters 13
1. Read Oracle assignment and create a script file Oracle_ch13_Lname_Fname.sql for questions (#1-5 and 9,10; p.508) on “Hands-on Assignments”.
2. Execute and test one problem at a time and make sure they are all running successfully.
3. When you done, spool the script files (see next slide for spooling instructions) and the file (Oracle_ch13_Spool_Lname_Fname.txt) to me by the midnight before the next class.

43. How to Spool your Script and Output Files
After you tested the script file of Oracle_ch13_Lname_Fname.sql successfully, follow the instructions below to spool both script and output files:
Step 0. Run the following script file from SQL*Plus (since you have created JLDB tables)
1. type the following on SQL>
Spool c:\oradata\Oracle_ch13B_Spool_Lname_Fname.txt (make sure your name is entered)
2. open Oracle_ch13_Lname_Fname.sql that you already tested
3. copy and paste all the SQL commands (including all comments) to the SQL*PLUS
4. type Spool Off on the SQL>
The output should contain your personal information, all SQL commands and their solution on the .txt file and saved in C: drive (oradata\ folder)
me with the spooled file (.txt) with attachment to:
with subject title of
Bmis441-01_Oracle_ch13 (or Bmis441-02_Oracle_ch13)

44. PART III

45. Materialized Views
Replicate data
Store data retrieved from view query
Referred to as “snapshots”

46. Materialized Views (continued)
Figure Creating a materialized view named CUSTBAL_MV

47. Figure 13-31 Query a materialized view

48. Materialized Views (continued)
Figure Drop a materialized view

49. Summary
A view is a temporary or virtual table that is used to retrieve data that exists in the underlying database tables
The view query must be executed each time the view is used
A view can be used to simplify queries or to restrict access to sensitive data
A view is created with the CREATE VIEW command
A view cannot be modified; to change a view, it must be dropped and then re-created, or the CREATE OR REPLACE VIEW command must be used

50. Summary (continued)
Any DML operation can be performed on a simple query if it does not violate a constraint
A view that contains expressions or functions, or that joins multiple tables, is considered a complex view
A complex view can be used to update only one table; the table must be a key-preserved table
Data cannot be added to a view column that contains an expression
DML operations are not permitted on non-key-preserved tables

51. Summary (continued)
DML operations are not permitted on views that include group functions, a GROUP BY clause, the ROWNUM pseudocolumn, or the DISTINCT keyword
Oracle 11g assigns a row number to every row in a table to indicate its position in the table; the row number can be referenced by the keyword ROWNUM
A view can be dropped with the DROPVIEW command; the data is not affected, because it exists in the original tables
An inline view can be used only by the current statement and can include an ORDER BY clause
“TOP-N” analysis uses the row number of sorted data to determine a range of top values
Materialized views physically store view query results