Views with CHECK OPTION in PostgreSQL - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to create a view that only shows employees from the 'Sales' department.

PostgreSQL

CREATE VIEW sales_employees AS SELECT * FROM employees WHERE department = [1];

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

A'HR'

B'Marketing'

C'Sales'

D'Finance'

Attempts:

3 left

💡 Hint

Common Mistakes

Forgetting the single quotes around the department name.

Using the wrong department name.

The view filters employees to only those in the 'Sales' department by using the WHERE clause with 'Sales'.

2fill in blank

medium

Complete the code to add WITH CHECK OPTION to the view to prevent inserts or updates outside 'Sales'.

PostgreSQL

CREATE VIEW sales_employees AS SELECT * FROM employees WHERE department = 'Sales' [1];

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

AWITH READ ONLY

BWITH CHECK OPTION

CWITH NO CHECK

DWITH UPDATE OPTION

Attempts:

3 left

💡 Hint

Common Mistakes

Using WITH READ ONLY which disallows all modifications.

Using incorrect or non-existent options.

WITH CHECK OPTION ensures that any insert or update through the view must satisfy the view's WHERE condition.

3fill in blank

hard

Fix the error in the view creation by choosing the correct placement of WITH CHECK OPTION.

PostgreSQL

CREATE VIEW sales_employees AS SELECT * FROM employees WHERE department = 'Sales' [1] WITH CHECK OPTION;

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

ANO

BAFTER

CBETWEEN

DBEFORE

Attempts:

3 left

💡 Hint

Common Mistakes

Placing WITH CHECK OPTION in the wrong position causing syntax errors.

Adding extra keywords before WITH CHECK OPTION.

WITH CHECK OPTION must come at the end of the CREATE VIEW statement, not before or after the SELECT clause.

4fill in blank

hard

Fill both blanks to create a view that shows only active products and enforces this with CHECK OPTION.

PostgreSQL

CREATE VIEW active_products AS SELECT * FROM products WHERE status = [1] [2];

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

A'active'

B'inactive'

CWITH CHECK OPTION

DWITH READ ONLY

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'inactive' instead of 'active' in the WHERE clause.

Using WITH READ ONLY which disallows all modifications.

The view filters products with status 'active' and uses WITH CHECK OPTION to prevent changes that violate this condition.

5fill in blank

hard

Fill all three blanks to create a view for employees in 'HR' department with salary over 50000 and enforce it with CHECK OPTION.

PostgreSQL

CREATE VIEW hr_high_salary AS SELECT * FROM employees WHERE department = [1] AND salary > [2] [3];

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

A'HR'

B50000

CWITH CHECK OPTION

D'Sales'

Attempts:

3 left

💡 Hint

Common Mistakes

Using wrong department name or salary value.

Forgetting to add WITH CHECK OPTION or placing it incorrectly.

The view filters employees in 'HR' with salary over 50000 and uses WITH CHECK OPTION to enforce this on inserts and updates.

Practice

1. What is the main purpose of using WITH CHECK OPTION in a PostgreSQL view?

easy

A. To prevent inserts or updates that violate the view's filter conditions

B. To speed up query execution on the view

C. To allow views to be updated without restrictions

D. To create a temporary table instead of a view

Solution

1. Step 1: Understand the role of WITH CHECK OPTION

   This option ensures that any data inserted or updated through the view must satisfy the view's filter conditions.

2. Step 2: Identify what it prevents

   It prevents changes that would cause rows to fall outside the view's defined criteria, keeping data consistent.

3. Final Answer:

   To prevent inserts or updates that violate the view's filter conditions -> Option A

4. Quick Check:

   WITH CHECK OPTION blocks invalid changes = A [OK]

Hint: Check option stops changes outside view filters [OK]

Common Mistakes:

• Thinking it speeds up queries
• Believing it allows unrestricted updates
• Confusing it with temporary tables

2. Which of the following is the correct syntax to create a view with a WITH CHECK OPTION in PostgreSQL?

easy

A. CREATE VIEW v AS SELECT * FROM t WHERE x > 10, WITH CHECK OPTION;

B. CREATE VIEW v AS SELECT * FROM t WHERE x > 10 CHECK OPTION WITH;

C. CREATE VIEW v AS SELECT * FROM t WHERE x > 10 WITH CHECK OPTION;

D. CREATE VIEW v AS SELECT * FROM t WHERE x > 10 OPTION CHECK WITH;

Solution

1. Step 1: Recall PostgreSQL view creation syntax

   The correct syntax places WITH CHECK OPTION at the end of the CREATE VIEW statement.

2. Step 2: Match the exact phrase and order

   CREATE VIEW v AS SELECT * FROM t WHERE x > 10 WITH CHECK OPTION; matches the correct syntax: CREATE VIEW v AS SELECT ... WITH CHECK OPTION;

3. Final Answer:

   CREATE VIEW v AS SELECT * FROM t WHERE x > 10 WITH CHECK OPTION; -> Option C

4. Quick Check:

   Correct syntax ends with WITH CHECK OPTION [OK]

Hint: WITH CHECK OPTION always goes at the end of CREATE VIEW [OK]

Common Mistakes:

• Swapping words order
• Adding semicolons inside SELECT
• Using incorrect keywords order

3. Given the table employees(id, name, salary) and the view:
CREATE VIEW high_salary AS SELECT * FROM employees WHERE salary > 5000 WITH CHECK OPTION;
What happens if you try to insert (10, 'Anna', 4000) into high_salary?

medium

A. The insert fails due to the CHECK OPTION

B. The insert succeeds but the row is not visible in the view

C. The insert succeeds and adds the row

D. The insert causes a syntax error

Solution

1. Step 1: Understand the view filter and CHECK OPTION

   The view only shows employees with salary > 5000, and WITH CHECK OPTION prevents inserts that don't meet this.

2. Step 2: Analyze the insert data

   The salary 4000 is less than 5000, so the insert violates the view's filter and is blocked.

3. Final Answer:

   The insert fails due to the CHECK OPTION -> Option A

4. Quick Check:

   Insert violating view filter blocked = C [OK]

Hint: Insert must meet view filter or it fails [OK]

Common Mistakes:

• Thinking insert always succeeds
• Assuming row is added but hidden
• Confusing syntax error with runtime error

4. You have this view:
CREATE VIEW active_users AS SELECT * FROM users WHERE active = true WITH CHECK OPTION;
You try to update a row through the view to set active = false. What is the result?

medium

A. The update succeeds and changes the row

B. The update causes a syntax error

C. The update succeeds but the row disappears from the view

D. The update fails because it violates the CHECK OPTION

Solution

1. Step 1: Understand the view filter and update

   The view only shows rows where active = true. WITH CHECK OPTION blocks updates that break this condition.

2. Step 2: Analyze the attempted update

   Setting active = false violates the view filter, so the update is rejected.

3. Final Answer:

   The update fails because it violates the CHECK OPTION -> Option D

4. Quick Check:

   Update violating view filter blocked = B [OK]

Hint: Updates must keep rows inside view filter [OK]

Common Mistakes:

• Assuming update succeeds but hides row
• Confusing syntax error with constraint error
• Ignoring CHECK OPTION effect on updates

5. Consider a view CREATE VIEW vip_customers AS SELECT * FROM customers WHERE vip = true WITH CHECK OPTION;
You want to allow inserting new customers through this view only if they are VIPs. Which of the following statements correctly inserts a VIP customer and rejects a non-VIP customer?

hard

A. INSERT INTO vip_customers (id, name, vip) VALUES (1, 'John', false); -- failsINSERT INTO vip_customers (id, name, vip) VALUES (2, 'Jane', false); -- fails

B. INSERT INTO vip_customers (id, name, vip) VALUES (1, 'John', true); -- succeedsINSERT INTO vip_customers (id, name, vip) VALUES (2, 'Jane', false); -- fails

C. INSERT INTO vip_customers (id, name, vip) VALUES (1, 'John', true); -- failsINSERT INTO vip_customers (id, name, vip) VALUES (2, 'Jane', false); -- succeeds

D. INSERT INTO vip_customers (id, name, vip) VALUES (1, 'John', false); -- succeedsINSERT INTO vip_customers (id, name, vip) VALUES (2, 'Jane', true); -- fails

Solution

1. Step 1: Understand the view filter and CHECK OPTION

   The view only allows rows where vip = true. WITH CHECK OPTION blocks inserts with vip = false.

2. Step 2: Analyze each insert statement

   Inserting John with vip = true succeeds. Inserting Jane with vip = false fails due to CHECK OPTION.

3. Final Answer:

   Only inserts with vip = true succeed; others fail -> Option B

4. Quick Check:

   Insert vip=true allowed, vip=false blocked = D [OK]

Hint: Only insert rows matching view filter pass CHECK OPTION [OK]

Common Mistakes:

• Trying to insert non-VIP through VIP view
• Assuming all inserts succeed
• Confusing which values pass CHECK OPTION