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IT420: Database Management and
SQL Views Organization

SQL Views (Chapter 7)

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SQL Views CREATE VIEW Command

SQL view is a virtual table that is constructed from other
CREATE VIEW command: tables or views CREATE VIEW view_name
It has no data of its own, but obtains data from tables or AS other views select_statement
It only has a definition
Use the view:
SELECT statements are used to define views
In SELECT statements
A view definition may not include an ORDER BY clause
Sometimes in INSERT statements
Views can be used as regular tables in SELECT
Sometimes in UPDATE statements statements
Sometimes in DELETE statements

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1 CREATE VIEW Command Uses for SQL Views

CREATE VIEW
Security: hide columns and rows command: CREATE VIEW CustomerNameView
Display results of computations AS
Hide complicated SQL syntax SELECT CustName AS CustomerName
Provide a level of isolation between actual FROM CUSTOMER; data and the user’s view of data
To use the view:
three-tier architecture SELECT *
Assign different processing permissions to FROM CustomerNameView ORDER BY CustomerName; different views on same table

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Security: hide columns and rows Display results of computations

MIDS database, Midshipmen table
Faculty (EmpID , LName, FName, Department, AreaCode, LocalPhone)
View for faculty – all mids with IT major
Create a view to display 2 columns:
View for students – all mids, no grades
Name = Fname LName
Midshipmen (Alpha , Name, DateOfBirth, GPA,
Phone = (AreaCode) LocalPhone Major)
SELECT, INSERT, UPDATE, DELETE?
Exercise: Write the SQL to create the views
SELECT, INSERT, UPDATE, DELETE?

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2 Provide a level of isolation between Hide complicated SQL syntax actual data and application
Mid(Alpha , LName, FName, Class, Age)
CREATE VIEW CustomerV AS
Course(CourseID , Description, Textbook) SELECT *
Enroll(Alpha , CourseID , Semester , Grade) FROM Customers
Applications use CustomerV
Create a view to display the student alpha,
Can change the underlying table without name, CourseID and description of courses they changing the application are/were enrolled ALTER VIEW CustomerV AS
SELECT, INSERT, UPDATE, DELETE? SELECT * FROM New_Customers

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Updating Views Updateable Views

CREATE VIEW CustomerV AS
Views based on a single table SELECT * FROM Customers
No computed columns
SELECT, INSERT, DELETE, UPDATE?
All non-null columns present in view

Faculty (EmpID, LName, FName, Department, AreaCode, LocalPhone)
CREATE VIEW FacultyPhone AS SELECT FName + ‘ ’ + LName AS Name, ‘(’ + AreaCode + ‘)’ + LocalPhone AS Phone
Views based on a single table, primary key in FROM Students view, some non-null columns missing from view

UPDATE FacultyPhone
Updates for non-computed columns ok SET Phone = ‘(410)-293-6822’ Works?
Deletes ok WHERE Name=‘Adina Crainiceanu’
Inserts not ok

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3 Summary – SQL Views

CREATE VIEW view_name AS select_statement
Virtual table
It only has a definition
Data is computed at run-time from base tables
All views can be used in SELECT
Some views can be used in INSERT, DELETE, UPDATE

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