chapter 13 views (up to p.495)

Dr. Chen, Oracle Database System (Oracle) 1

Chapter 13Views

(up to p.519)

Jason C. H. Chen, Ph.D.Professor of MIS

School of BusinessGonzaga University

Spokane, WA 99258 [email protected]


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


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


Database Views

Table-1 Table-NTable-2

database

Single view table

Query

Output:Report, Graphs

Database view

A database view is a logical (virtual) table based on a query.

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.


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


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


Database View (cont.)

h SELECT view_name FROM user_views;h SELECT view_name FROM ALL_VIEWS WHERE owner=‘SYSTEM’;h DROP VIEW <view_name>;h CREATE OR REPLACE VIEW <view_name> AS <view query specification>;


Types of Views

Table 13-1 Overview of View Concepts


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 13-2 Syntax of the CREATE VIEW command


CREATE OR REPLACE VIEW book_vu ASSELECT isbn, title, categoryFROM booksWHERE category = 'COOKING';

SELECT * FROM book_vu;

SQL> SELECT * 2 FROM book_vu;

ISBN TITLE CATEGORY---------- ------------------------------ ---------3437212490 COOKING WITH MUSHROOMS COOKING0299282519 THE WOK WAY TO COOK COOKING

See next slide for detailed process


FROM clause in query references a view rather than a table

SELECT* FROM book_vu;

BOOK_VU view(view stored in database)

Processing steps:1. A query references a view rather than a table in the FROM clause.2. The query stored in the view is executed.3. The results from the view query are stored in temporary storage.4. The original query uses the temporary query results of the view as a table and

completes execution.

2

Stores query:

SELECT isbn, title, category FROM books WHERE category=‘COOKING’;

1

3

4

Figure 13-1 View Processing


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.502CREATE VIEW region_neAS SELECT * FROM customers WHERE region = 'NE'; SELECT customer#, lastname, city, state, regionFROM region_ne;

-- chapter 13, Figure 13-4; p.501CREATE VIEW inventoryAS SELECT isbn, title, retail price FROM booksWITH READ ONLY;

SELECT *FROM inventory;


Why Failed to Update?-- chapter 13, Figure 13-6; p.503UPDATE inventory SET price = 45.96 WHERE title LIKE '%POEM';

-- “SELECT” is working (READ)SELECT * FROM inventory WHERE title LIKE '%POEM%';

UPDATE inventorySET title = 'THE SHORTEST POEMS'WHERE title LIKE '%POEM%';

Figure 13-6 Failed updates on the INVENTORY view

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---------- ------------------ ----------2147428890 SHORTEST POEMS 39.95

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


Combining Topics – VIEW and NON-Equality Join

• Combing both VIEW (chapter 13) and NON-EQUALITY JOINS (chapter 9; p.316)

• 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


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 0 12BOOK LABELS 12.01 25BOOK COVER 25.01 56FREE SHIPPING 56.01 999.99


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.


-- First Create VIEW for ‘book’ and publisherCREATE OR REPLACE VIEW book_profit_vu ASSELECT 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 22 7.8HOW TO MANAGE THE MANAGER PRINTING IS US 31.95 16.55E-BUSINESS THE EASY WAY PUBLISH OUR WAY 54.5 16.6BUILDING A CAR WITH TOOTHPICKS PUBLISH OUR WAY 59.95 22.15HOLY GRAIL OF ORACLE AMERICAN PUBLISHING 75.95 28.7DATABASE IMPLEMENTATION AMERICAN PUBLISHING 55.95 24.55HANDCRANKED COMPUTERS AMERICAN PUBLISHING 25 3.2COOKING WITH MUSHROOMS READING MATERIALS INC. 19.95 7.45THE WOK WAY TO COOK READING MATERIALS INC. 28.75 9.75HOW TO GET FASTER PIZZA READING MATERIALS INC. 29.95 12.1BODYBUILD IN 10 MINUTES A DAY READING MATERIALS INC. 30.95 12.2PAINLESS CHILD-REARING REED-N-RITE 89.95 41.95BIG BEAR AND LITTLE DOVE REED-N-RITE 8.95 3.63SHORTEST POEMS REED-N-RITE 39.95 18.1

14 rows selected.

pk

fk


-- use "NON-EQUALITY JOIN" (p.316)SELECT title, Publisher_name, retail, p.gift, TO_CHAR(profit, '$999.99') ProfitFROM book_profit_vu bpvu, promotion pWHERE bpvu.retail ___________ p.minretail ______ p.maxretailORDER BY profit;

column title format A23COLUMN name format A18column proft format $999.99column retail format $999.99column gift format A13

SELECT title, Publisher_name, retail, p.gift, TO_CHAR(profit, '$999.99') ProfitFROM book_profit_vu bpvu, promotion pWHERE bpvu.retail BETWEEN p.minretail AND p.maxretail ORDER BY profit;

BETWEEN AND


TITLE PUBLISHER_NAME RETAIL GIFT PROFIT----------------------- ----------------------- -------- ------------- --------HANDCRANKED COMPUTERS AMERICAN PUBLISHING $25.00 BOOK LABELS $3.20BIG BEAR AND LITTLE DOV REED-N-RITE $8.95 BOOKMARKER $3.63E

COOKING WITH MUSHROOMS READING MATERIALS INC. $19.95 BOOK LABELS $7.45REVENGE OF MICKEY PRINTING IS US $22.00 BOOK LABELS $7.80THE WOK WAY TO COOK READING MATERIALS INC. $28.75 BOOK COVER $9.75HOW TO GET FASTER PIZZA READING MATERIALS INC. $29.95 BOOK COVER $12.10BODYBUILD IN 10 MINUTES READING MATERIALS INC. $30.95 BOOK COVER $12.20 A DAYHOW TO MANAGE THE MANAG PRINTING IS US $31.95 BOOK COVER $16.55ER

E-BUSINESS THE EASY WAY PUBLISH OUR WAY $54.50 BOOK COVER $16.60SHORTEST POEMS REED-N-RITE $39.95 BOOK COVER $18.10BUILDING A CAR WITH TOO PUBLISH OUR WAY $59.95 FREE SHIPPING $22.15THPICKS

DATABASE IMPLEMENTATION AMERICAN PUBLISHING $55.95 BOOK COVER $24.55HOLY GRAIL OF ORACLE AMERICAN PUBLISHING $75.95 FREE SHIPPING $28.70PAINLESS CHILD-REARING REED-N-RITE $89.95 FREE SHIPPING $41.95

14 rows selected. GIFT MINRETAIL MAXRETAIL--------------- ---------- ----------BOOKMARKER 0 12BOOK LABELS 12.01 25BOOK COVER 25.01 56FREE SHIPPING 56.01 999.99


A Version without VIEW

--1c.(TRADITIONAL JOIN; modified version from p.316)

SELECT b.title, pu.name "Publisher Name", b.retail, p.gift, b.retail-b.cost proftFROM books b, publisher pu, promotion pWHERE b.pubid = pu.pubid AND b.retail BETWEEN p.minretail AND p.maxretail ORDER BY b.retail-b.cost;


-- chapter 13, Figure 13-7; p.504CREATE OR REPLACE VIEW inventoryAS SELECT isbn, title, retail price FROM books; SELECT *FROM inventoryWHERE title LIKE '%BODYBUILD%';

-- chapter 13, Figure 13-8; p.505UPDATE inventorySET price = 49.95WHERE title LIKE '%BODYBUILD%';

SELECT *FROM inventoryWHERE title LIKE '%BODYBUILD%';

SELECT *FROM booksWHERE title LIKE '%BODYBUILD%';

DML Operations on a Simple View (continued)


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 13-11 (pp.506-507)


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 contactAS SELECT contact, phone FROM publisher;


Homework - Hands-On Assignments

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.537) 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 the file (Oracle_ch13_Spool_Lname_Fname.txt) to me by the midnight Sunday.

• 4. Turn in a hardcopy next class.

Upload the source (*.sql) and spooled file (*.txt) to the Bb (under “Assignments & Projects”) by the deadline.


How to Spool your Script and Output FilesAfter 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)


• PART II

chapter 13 views (up to p.495)

Documents