Updatable views in MySQL - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to create a simple updatable view showing employee names and salaries.

MySQL

CREATE VIEW employee_salaries AS SELECT name, [1] FROM employees;

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

Aid

Bage

Cdepartment

Dsalary

Attempts:

3 left

💡 Hint

Common Mistakes

Choosing a column unrelated to salary like age or department.

Selecting the employee ID instead of salary.

The view should select the salary column to show employee salaries.

2fill in blank

medium

Complete the code to update the salary of an employee through the view.

MySQL

UPDATE employee_salaries SET [1] = 60000 WHERE name = 'John';

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

Aname

Bid

Csalary

Ddepartment

Attempts:

3 left

💡 Hint

Common Mistakes

Trying to update the name or department instead of salary.

Using the employee ID which is not shown in the view.

To update the salary, set the salary column in the view.

3fill in blank

hard

Fix the error in the view definition to make it updatable by removing the aggregate function.

MySQL

CREATE VIEW avg_salary AS SELECT department, [1] FROM employees;

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

Asalary

BAVG

CMAX

DSUM

Attempts:

3 left

💡 Hint

Common Mistakes

Leaving the AVG function which prevents updates.

Replacing AVG with another aggregate function like SUM or MAX.

Aggregate functions like AVG make views non-updatable. Use the raw column salary instead.

4fill in blank

hard

Fill both blanks to create an updatable view that filters employees by department.

MySQL

CREATE VIEW [1] AS SELECT name, salary FROM employees WHERE [2] = 'Sales';

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

Asales_employees

Bdepartment

Csalary

Demployee_name

Attempts:

3 left

💡 Hint

Common Mistakes

Using a generic or unrelated view name.

Filtering by salary or name instead of department.

The view name should reflect its content, like sales_employees. The filter column is department.

5fill in blank

hard

Fill all three blanks to create an updatable view that shows employee names in uppercase and filters by salary.

MySQL

CREATE VIEW [1] AS SELECT [2](name) AS name_upper, salary FROM employees WHERE salary [3] 50000;

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

Ahigh_earners

BUPPER

C>

DLOWER

Attempts:

3 left

💡 Hint

Common Mistakes

Using LOWER instead of UPPER for name conversion.

Using <= or < instead of > for the salary filter.

The view is named high_earners to reflect the salary filter. Use UPPER to convert names to uppercase. The filter uses > to select salaries above 50000.

Practice

1. What is an updatable view in MySQL?

easy

A. A view that only shows data but does not allow any changes.

B. A view that allows you to change the data in the underlying table through it.

C. A view that automatically creates new tables.

D. A view that stores data separately from the original table.

Solution

1. Step 1: Understand what a view is

   A view is a saved query that shows data from one or more tables.

2. Step 2: Define updatable view

   An updatable view lets you change data in the underlying table through the view itself.

3. Final Answer:

   A view that allows you to change the data in the underlying table through it. -> Option B

4. Quick Check:

   Updatable view = allows data change [OK]

Hint: Updatable views let you edit data through the view [OK]

Common Mistakes:

• Thinking views store data separately
• Confusing read-only views with updatable views
• Assuming all views are updatable

2. Which of the following is the correct syntax to create an updatable view in MySQL?

easy

A. CREATE VIEW view_name UPDATEABLE AS SELECT * FROM table_name;

B. CREATE UPDATABLE VIEW view_name AS SELECT * FROM table_name;

C. CREATE VIEW view_name WITH UPDATE AS SELECT * FROM table_name;

D. CREATE VIEW view_name AS SELECT * FROM table_name;

Solution

1. Step 1: Recall MySQL view creation syntax

   MySQL uses CREATE VIEW view_name AS SELECT ... to create views.

2. Step 2: Understand updatable views syntax

   There is no special keyword for updatable views; they are updatable if the SELECT is simple enough.

3. Final Answer:

   CREATE VIEW view_name AS SELECT * FROM table_name; -> Option D

4. Quick Check:

   Standard CREATE VIEW syntax = CREATE VIEW view_name AS SELECT * FROM table_name; [OK]

Hint: No special keyword needed; simple CREATE VIEW works [OK]

Common Mistakes:

• Adding non-existent keywords like UPDATABLE or WITH UPDATE
• Using wrong syntax keywords
• Assuming updatable views need special creation syntax

3. Given the table employees(id, name, salary) and the view:
CREATE VIEW emp_view AS SELECT id, name FROM employees;
Which of the following statements will succeed?

medium

A. UPDATE emp_view SET name = 'Alice' WHERE id = 1;

B. INSERT INTO emp_view (id, name) VALUES (4, 'Bob');

C. DELETE FROM emp_view WHERE salary = 2000;

D. UPDATE emp_view SET salary = 5000 WHERE id = 3;

Solution

1. Step 1: Check view columns and underlying table

   The view selects only id and name, excluding salary.

2. Step 2: Determine which operations are allowed

   Updating name through the view is allowed because it maps directly to the table column.
   INSERT fails (missing salary, assuming NOT NULL no default).
   DELETE referencing salary fails because salary not in view.
   Updating salary fails because salary not in view.

3. Final Answer:

   UPDATE emp_view SET name = 'Alice' WHERE id = 1; -> Option A

4. Quick Check:

   Update on view columns allowed = UPDATE emp_view SET name = 'Alice' WHERE id = 1; [OK]

Hint: You can update only columns included in the view [OK]

Common Mistakes:

• Trying to update columns not in the view
• Assuming inserts/deletes always work on views
• Ignoring missing columns in the view

4. You created a view with:
CREATE VIEW v AS SELECT id, name FROM employees WHERE salary > 3000;
Why does the statement UPDATE v SET salary = 5000 WHERE id = 5; fail?

medium

A. Because the view does not include the salary column.

B. Because the view has a WHERE clause, making it non-updatable.

C. Because you cannot update views with more than one column.

D. Because the view name is invalid.

Solution

1. Step 1: Check the columns in the view and the UPDATE target

   The view selects only id and name; salary is excluded.

2. Step 2: Check other options

   A WHERE clause does not prevent updates to included columns.
   Views can have multiple columns and be updatable.
   The view name is valid.

3. Final Answer:

   Because the view does not include the salary column. -> Option A

4. Quick Check:

   Cannot update column not in view [OK]

Hint: Cannot modify columns absent from the view [OK]

Common Mistakes:

• Thinking WHERE clause blocks updates
• Assuming multiple columns prevent updates
• Ignoring missing columns in the view

5. You want to create an updatable view on the orders table that shows only order_id and customer_id. You also want to allow updates to customer_id through the view. Which of the following is the best approach?

hard

A. CREATE VIEW order_view AS SELECT order_id FROM orders; Then update customer_id through order_view.

B. CREATE VIEW order_view AS SELECT order_id, customer_id FROM orders WHERE order_date > '2023-01-01'; Then update customer_id through order_view.

C. CREATE VIEW order_view AS SELECT order_id, customer_id FROM orders; Then update customer_id through order_view.

D. CREATE VIEW order_view AS SELECT order_id, customer_id, total FROM orders; Then update customer_id through order_view.

Solution

1. Step 1: Identify columns needed in the view

   The view must include customer_id to allow updates on it.

2. Step 2: Avoid issues that limit updatability or scope

   Adding a WHERE clause (as in B) limits updates to only recent orders.
   Including extra columns (as in C) shows more than requested.
   Excluding customer_id (as in A) prevents updating it.
   D provides exactly the requested columns without restrictions.

3. Final Answer:

   CREATE VIEW order_view AS SELECT order_id, customer_id FROM orders; Then update customer_id through order_view. -> Option C

4. Quick Check:

   Simple view with needed columns = updatable [OK]

Hint: Include columns to update, avoid WHERE filters [OK]

Common Mistakes:

• Adding WHERE filters that limit updates
• Excluding columns you want to update
• Adding unnecessary columns that confuse