Views for security and abstraction in SQL - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to create a view named 'employee_view' that shows only the 'name' and 'salary' columns from the 'employees' table.

SQL

CREATE VIEW employee_view AS SELECT [1] FROM employees;

Drag options to blanks, or click blank then click option'

Aid, department

Bsalary, department

C*

Dname, salary

Attempts:

3 left

💡 Hint

Common Mistakes

Using '*' selects all columns, which is not secure.

Selecting columns not needed in the view.

The view should include only the 'name' and 'salary' columns, so the SELECT statement must specify these columns.

2fill in blank

medium

Complete the code to select all data from the view named 'employee_view'.

SQL

SELECT [1] FROM employee_view;

Drag options to blanks, or click blank then click option'

A*

Bname, salary

Cid

Ddepartment

Attempts:

3 left

💡 Hint

Common Mistakes

Selecting columns not present in the view.

Using column names instead of '*'.

Using '*' selects all columns available in the view.

3fill in blank

hard

Fix the error in the code that tries to create a view with a WHERE clause filtering salary greater than 50000.

SQL

CREATE VIEW high_salary_view AS SELECT name, salary FROM employees WHERE salary [1] 50000;

Drag options to blanks, or click blank then click option'

A=

B<=

C>

D<

Attempts:

3 left

💡 Hint

Common Mistakes

Using '=' selects only salaries exactly 50000.

Using '<' or '<=' selects lower salaries.

The condition should filter salaries greater than 50000, so the operator must be '>'.

4fill in blank

hard

Fill both blanks to create a view named 'dept_view' that shows 'name' and 'department' columns only for employees in the 'Sales' department.

SQL

CREATE VIEW dept_view AS SELECT [1] FROM employees WHERE [2] = 'Sales';

Drag options to blanks, or click blank then click option'

Aname, department

Bsalary

Cdepartment

Did

Attempts:

3 left

💡 Hint

Common Mistakes

Selecting columns not needed in the view.

Filtering on the wrong column.

The view should show 'name' and 'department' columns, and filter rows where 'department' equals 'Sales'.

5fill in blank

hard

Fill all three blanks to create a view named 'secure_view' that shows uppercase employee names, their salary, and filters salaries greater than 60000.

SQL

CREATE VIEW secure_view AS SELECT [1] AS name_upper, [2] FROM employees WHERE [3] > 60000;

Drag options to blanks, or click blank then click option'

AUPPER(name)

Bsalary

Dname

Attempts:

3 left

💡 Hint

Common Mistakes

Not using UPPER() for the name.

Filtering on the wrong column or using wrong operator.

The view selects the uppercase version of 'name' as 'name_upper', includes 'salary', and filters salaries greater than 60000.

Practice

1. What is the main purpose of using a VIEW in SQL?

easy

A. To permanently store data in the database

B. To provide a simplified and secure way to access specific data

C. To create a backup of the database

D. To speed up the database server hardware

Solution

1. Step 1: Understand what a VIEW is

   A VIEW is a virtual table created by a SELECT query that shows data without storing it separately.

2. Step 2: Identify the purpose of a VIEW

   It helps users see only the data they need, hiding sensitive details and simplifying complex queries.

3. Final Answer:

   To provide a simplified and secure way to access specific data -> Option B

4. Quick Check:

   VIEW = Simplify + Secure access [OK]

Hint: Views show selected data safely without storing it separately [OK]

Common Mistakes:

• Thinking views store data permanently
• Confusing views with backups
• Believing views improve hardware speed

2. Which of the following is the correct syntax to create a view named EmployeeView showing only EmployeeID and Name from Employees table?

easy

A. CREATE VIEW EmployeeView AS SELECT EmployeeID, Name FROM Employees;

B. MAKE VIEW EmployeeView SELECT EmployeeID, Name FROM Employees;

C. CREATE TABLE EmployeeView AS SELECT EmployeeID, Name FROM Employees;

D. VIEW CREATE EmployeeView SELECT EmployeeID, Name FROM Employees;

Solution

1. Step 1: Recall the correct SQL syntax for creating a view

   The syntax is: CREATE VIEW view_name AS SELECT columns FROM table;

2. Step 2: Match the syntax with options

   CREATE VIEW EmployeeView AS SELECT EmployeeID, Name FROM Employees; matches the correct syntax exactly.

3. Final Answer:

   CREATE VIEW EmployeeView AS SELECT EmployeeID, Name FROM Employees; -> Option A

4. Quick Check:

   CREATE VIEW ... AS SELECT ... [OK]

Hint: Use CREATE VIEW ... AS SELECT ... to define views [OK]

Common Mistakes:

• Using MAKE VIEW instead of CREATE VIEW
• Confusing CREATE VIEW with CREATE TABLE
• Incorrect keyword order

3. Given the table Employees with columns EmployeeID, Name, Salary, and a view EmployeeView defined as:

CREATE VIEW EmployeeView AS SELECT EmployeeID, Name FROM Employees;

What will the query SELECT * FROM EmployeeView; return?

medium

A. Only Salary column

B. All columns: EmployeeID, Name, Salary

C. Only EmployeeID and Name columns

D. Syntax error because Salary is missing

Solution

1. Step 1: Understand the view definition

   The view selects only EmployeeID and Name columns from Employees.

2. Step 2: Determine what SELECT * from the view returns

   It returns only the columns defined in the view, which are EmployeeID and Name.

3. Final Answer:

   Only EmployeeID and Name columns -> Option C

4. Quick Check:

   View columns = Selected columns only [OK]

Hint: View shows only columns defined in its SELECT query [OK]

Common Mistakes:

• Expecting all original table columns
• Thinking missing columns cause syntax errors
• Confusing view columns with table columns

4. Consider this incorrect SQL statement to create a view:

CREATE VIEW SalesView SELECT OrderID, Amount FROM Sales;

What is the error and how to fix it?

medium

A. Incorrect view name; fix by renaming view

B. Missing FROM keyword; fix by adding FROM before Sales

C. SELECT statement is not allowed in views

D. Missing AS keyword; fix by adding AS after view name

Solution

1. Step 1: Identify the syntax error in CREATE VIEW

   The correct syntax requires AS keyword after the view name.

2. Step 2: Correct the statement

   Add AS after SalesView: CREATE VIEW SalesView AS SELECT OrderID, Amount FROM Sales;

3. Final Answer:

   Missing AS keyword; fix by adding AS after view name -> Option D

4. Quick Check:

   CREATE VIEW ... AS SELECT ... [OK]

Hint: Always use AS after view name in CREATE VIEW [OK]

Common Mistakes:

• Omitting AS keyword
• Misplacing FROM keyword
• Thinking SELECT is disallowed in views

5. You want to create a view PublicEmployeeData that hides the Salary column from the Employees table but allows users to see EmployeeID, Name, and Department. Which SQL statement correctly creates this view and ensures security by restricting access to sensitive data?

hard

A. CREATE VIEW PublicEmployeeData AS SELECT EmployeeID, Name, Department FROM Employees;

B. CREATE VIEW PublicEmployeeData AS SELECT * FROM Employees WHERE Salary IS NULL;

C. CREATE VIEW PublicEmployeeData AS SELECT EmployeeID, Name, Department, Salary FROM Employees;

D. CREATE VIEW PublicEmployeeData AS SELECT EmployeeID, Name FROM Employees;

Solution

1. Step 1: Identify columns to include and exclude

   We want EmployeeID, Name, Department but NOT Salary to protect sensitive data.

2. Step 2: Choose the correct SELECT statement for the view

   CREATE VIEW PublicEmployeeData AS SELECT EmployeeID, Name, Department FROM Employees; selects only the allowed columns, hiding Salary effectively.

3. Final Answer:

   CREATE VIEW PublicEmployeeData AS SELECT EmployeeID, Name, Department FROM Employees; -> Option A

4. Quick Check:

   View excludes Salary to secure sensitive data [OK]

Hint: Select only non-sensitive columns in view to protect data [OK]

Common Mistakes:

• Including Salary column accidentally
• Using WHERE Salary IS NULL which filters rows, not columns
• Selecting too few columns missing Department