More on views Please refer to speaker notes for additional information!

SQL> CREATE VIEW stuview1 2 AS 3 SELECT name, s.majorcode, majorname 4 FROM student00 s, major00 m 5 WHERE s.majorcode = m.majorcode; View created. SQL> DESC stuview1; Name Null? Type NAME VARCHAR2(20) MAJORCODE VARCHAR2(2) MAJORNAME VARCHAR2(30) SQL> SELECT * FROM stuview1; NAME MA MAJORNAME Stephen Daniels BU Business Administration Jennifer Ames CI Computer Information Systems Carl Hersey BU Business Administration Mary Stanton CI Computer Information Systems John Richards CI Computer Information Systems Student view In this slide, I am creating a view with information from the student00 table and the major00 table.

Student view SQL> CREATE OR REPLACE VIEW stuview1 2 AS 3 SELECT name, s.majorcode, majorname, enrolled 4 FROM student00 s, major00 m 5 WHERE s.majorcode = m.majorcode; View created. SQL> DESC stuview1 Name Null? Type NAME VARCHAR2(20) MAJORCODE VARCHAR2(2) MAJORNAME VARCHAR2(30) ENROLLED DATE SQL> SELECT * FROM stuview1; NAME MA MAJORNAME ENROLLED Stephen Daniels BU Business Administration 09-SEP-00 Jennifer Ames CI Computer Information Systems 02-SEP-00 Carl Hersey BU Business Administration 02-SEP-00 Mary Stanton CI Computer Information Systems 05-SEP-00 John Richards CI Computer Information Systems 06-SEP-00 This allows you to create a new view or modify an existing view by replacing the specifications.

SQL> CREATE VIEW payview1 2 (empno, empname, empjobcode, empsalary, empbonus) 3 AS 4 SELECT pay_id, name, jobcode, salary, bonus 5 FROM first_pay 6 WHERE salary > 30000; View created. SQL> DESC payview1 Name Null? Type EMPNO VARCHAR2(4) EMPNAME VARCHAR2(20) EMPJOBCODE CHAR(2) EMPSALARY NUMBER(9,2) EMPBONUS NUMBER(5) SQL> SELECT * FROM payview1; EMPN EMPNAME EM EMPSALARY EMPBONUS Linda Costa CI John Davidson IN Stephen York CM Richard Jones CI Joanne Brown IN Donald Brown CI Paula Adams IN rows selected. Pay view New names are given to the columns/fields in the view. Pay_id will be come empno, name will become empname etc.

Pay view for update SQL> CREATE VIEW new_payview1 2 (empno, empname, empjobcode, empsalary, empbonus) 3 AS 4 SELECT pay_id, name, jobcode, salary, bonus 5 FROM new_first_pay 6 WHERE salary > 30000; I decided to modify new_first_pay, so I recreated the view from the previous slide and named it new_payview1. SQL> SELECT * FROM new_first_pay; PAY_ NAME JO STARTDATE SALARY BONUS Linda Costa CI 15-JAN John Davidson IN 25-SEP Susan Ash AP 05-FEB Stephen York CM 03-JUL Richard Jones CI 30-OCT Joanne Brown IN 18-AUG Donald Brown CI 05-NOV Paula Adams IN 12-DEC Joseph Souza IN SQL> SELECT * FROM new_payview1; EMPN EMPNAME EM EMPSALARY EMPBONUS Linda Costa CI John Davidson IN Stephen York CM Richard Jones CI Joanne Brown IN Donald Brown CI Paula Adams IN Joseph Souza IN 35000

Updating view SQL> SELECT * FROM new_payview1; EMPN EMPNAME EM EMPSALARY EMPBONUS Linda Costa CI John Davidson IN Stephen York CM Richard Jones CI Joanne Brown IN Donald Brown CI Paula Adams IN Joseph Souza IN rows selected. SQL> SELECT * FROM new_first_pay; PAY_ NAME JO STARTDATE SALARY BONUS Linda Costa CI 15-JAN John Davidson IN 25-SEP Susan Ash AP 05-FEB Stephen York CM 03-JUL Richard Jones CI 30-OCT Joanne Brown IN 18-AUG Donald Brown CI 05-NOV Paula Adams IN 12-DEC Joseph Souza IN rows selected. SQL> UPDATE new_payview1 2 SET empbonus = WHERE empno = '9999'; 1 row updated. The update statement updates the data in new_payview1 as shown. When the view is updated, it also updates the data in the original table.

SQL> SELECT * FROM empx; IDN NAME DE John Doe AP 222 Mary Jones AR 333 David Souza AP 444 Susan Brooks AR 555 Michael Brown IN SQL> SELECT * FROM deptx; DE DEPTNAME AP Acct Pay AR Acct Recv IN Inventory View with multiple tables SQL> CREATE VIEW empdeptx 2 AS 3 SELECT idno, name, empx.dept, deptname 4 FROM empx, deptx 5 WHERE empx.dept = deptx.dept; View created. SQL> SELECT * FROM empdeptx; IDN NAME DE DEPTNAME John Doe AP Acct Pay 333 David Souza AP Acct Pay 222 Mary Jones AR Acct Recv 444 Susan Brooks AR Acct Recv 555 Michael Brown IN Inventory I created the two tables shown and then combined the information from the two tables into a view called empdeptx.

Update view SQL> UPDATE empx 2 SET name = 'John Adams' 3 WHERE idno = '111'; 1 row updated. SQL> SELECT * FROM empx; IDN NAME DE John Adams AP 222 Mary Jones AR 333 David Souza AP 444 Susan Brooks AR 555 Michael Brown IN SQL> SELECT * FROM empdeptx; IDN NAME DE DEPTNAME John Adams AP Acct Pay 333 David Souza AP Acct Pay 222 Mary Jones AR Acct Recv 444 Susan Brooks AR Acct Recv 555 Michael Brown IN Inventory In this example, I updated the table empx. The change in the table is also shown in the view.

SQL> CREATE VIEW new_payview2 2 AS 3 SELECT * FROM new_first_pay 4 WHERE salary > WITH CHECK OPTION CONSTRAINT sal30K_ck; View constraints SQL> UPDATE new_payview2 2 SET salary = WHERE pay_id = '9999'; SET salary = * ERROR at line 2: ORA-01402: view WITH CHECK OPTION where-clause violation SQL> UPDATE new_payview2 2 SET salary = WHERE pay_id = '9999'; 1 row updated. SQL> SELECT * FROM new_payview2; PAY_ NAME JO STARTDATE SALARY BONUS Linda Costa CI 15-JAN John Davidson IN 25-SEP Stephen York CM 03-JUL Richard Jones CI 30-OCT Joanne Brown IN 18-AUG Donald Brown CI 05-NOV Paula Adams IN 12-DEC Joseph Souza IN rows selected. I created a view with a constraint that did not allow a salary to be in the view that was not > Only records that met that criteria were originally placed in the view. When I tried to alter a record in the view to come in below the criteria, it was rejected as a check option violation. Here the new salary is above 30000, so the change is allowed.

SQL> SELECT * FROM new_first_pay; PAY_ NAME JO STARTDATE SALARY BONUS Linda Costa CI 15-JAN John Davidson IN 25-SEP Susan Ash AP 05-FEB Stephen York CM 03-JUL Richard Jones CI 30-OCT Joanne Brown IN 18-AUG Donald Brown CI 05-NOV Paula Adams IN 12-DEC Joseph Souza IN rows selected. SQL> SELECT * FROM new_payview2; PAY_ NAME JO STARTDATE SALARY BONUS Linda Costa CI 15-JAN John Davidson IN 25-SEP Stephen York CM 03-JUL Richard Jones CI 30-OCT Joanne Brown IN 18-AUG Donald Brown CI 05-NOV Paula Adams IN 12-DEC rows selected. SQL> UPDATE new_first_pay 2 SET SALARY = WHERE pay_id = '9999'; 1 row updated. Update In this example, I updated the table new_first_pay. The update was successful, but it put 9999 below the criteria for the view new_payview2. When I did a select on that view, the record with pay_id 9999 that now has a salary below the view criteria (salary > 30000) is no longer there.

SQL> CREATE VIEW new_payview3 2 AS 3 SELECT * FROM new_first_pay 4 WITH READ ONLY; View created. SQL> SELECT * FROM new_payview3; PAY_ NAME JO STARTDATE SALARY BONUS Linda Costa CI 15-JAN John Davidson IN 25-SEP Susan Ash AP 05-FEB Stephen York CM 03-JUL Richard Jones CI 30-OCT Joanne Brown IN 18-AUG Donald Brown CI 05-NOV Paula Adams IN 12-DEC Joseph Souza IN rows selected. SQL> UPDATE new_payview3 2 SET salary = WHERE pay_id = '2222'; SET salary = * ERROR at line 2: ORA-01733: virtual column not allowed here Read only Since this view was created as read only, it cannot be updated.

Drop view SQL> DROP VIEW new_payview3; View dropped. SQL> SELECT * FROM new_payview3; SELECT * FROM new_payview3 * ERROR at line 1: ORA-00942: table or view does not exist