CREATE VIEW syntax in SQL - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is a VIEW in SQL?

A VIEW is a virtual table based on the result of a SQL query. It does not store data itself but shows data from one or more tables.

beginner

Write the basic syntax to create a VIEW in SQL.

CREATE VIEW view_name AS SELECT column1, column2 FROM table_name WHERE condition;

intermediate

Can you update data through a VIEW?

Sometimes yes, if the VIEW is simple and directly maps to one table without complex joins or aggregations. Otherwise, updates are not allowed.

beginner

What happens if you try to SELECT from a VIEW?

The database runs the underlying query of the VIEW and returns the result as if it was a table.

beginner

How do you remove a VIEW from the database?

Use the command: DROP VIEW view_name;

What does the CREATE VIEW statement do?

A Inserts data into a table

B Deletes a table from the database

C Updates data in a table

D Creates a virtual table based on a SELECT query

CREATE VIEW defines a virtual table using a SELECT query.

Which keyword is used to define the columns shown in a VIEW?

A AS

B SELECT

C WHERE

D FROM

SELECT specifies the columns shown in a VIEW.

Can a VIEW contain data itself?

A Yes, but only temporary data

B Yes, it stores data permanently

C No, it only shows data from tables

D Only if created with INSERT

A VIEW does not store data; it shows data from underlying tables.

How do you delete a VIEW named 'employee_view'?

A DROP VIEW employee_view;

B DELETE VIEW employee_view;

C REMOVE VIEW employee_view;

D ERASE VIEW employee_view;

DROP VIEW is the correct command to remove a VIEW.

Which of these is a valid reason to use a VIEW?

A To simplify complex queries

B To permanently store data

C To speed up data insertion

D To delete tables

Views help simplify complex queries by encapsulating them.

Explain what a VIEW is and how to create one using SQL.

Think of a VIEW as a saved SELECT query that looks like a table.

Describe how you can use a VIEW and how to remove it when no longer needed.

Views are virtual tables you can query like real tables.

Practice

1. What is the main purpose of the CREATE VIEW statement in SQL?

easy

A. To save a SELECT query as a virtual table

B. To permanently store data in the database

C. To delete rows from a table

D. To update existing records in a table

Solution

1. Step 1: Understand what a view is

   A view is a virtual table created by saving a SELECT query.

2. Step 2: Identify the purpose of CREATE VIEW

   CREATE VIEW stores the SELECT query so you can use it like a table without storing data.

3. Final Answer:

   To save a SELECT query as a virtual table -> Option A

4. Quick Check:

   CREATE VIEW = virtual table [OK]

Hint: Views save SELECT queries as virtual tables [OK]

Common Mistakes:

• Thinking views store data physically
• Confusing CREATE VIEW with INSERT or UPDATE
• Assuming views delete or modify data

2. Which of the following is the correct syntax to create a view named EmployeeView that selects all columns from the Employees table?

easy

A. CREATE EmployeeView VIEW AS SELECT * FROM Employees;

B. CREATE VIEW EmployeeView AS SELECT * FROM Employees;

C. VIEW CREATE EmployeeView AS SELECT * FROM Employees;

D. CREATE VIEW Employees AS SELECT * FROM EmployeeView;

Solution

1. Step 1: Recall the correct CREATE VIEW syntax

   The syntax is: CREATE VIEW view_name AS SELECT ...

2. Step 2: Match the syntax with options

   CREATE VIEW EmployeeView AS SELECT * FROM Employees; matches the correct syntax exactly.

3. Final Answer:

   CREATE VIEW EmployeeView AS SELECT * FROM Employees; -> Option B

4. Quick Check:

   CREATE VIEW view_name AS SELECT ... [OK]

Hint: CREATE VIEW view_name AS SELECT ... [OK]

Common Mistakes:

• Swapping keywords CREATE and VIEW
• Mixing table and view names incorrectly
• Using wrong keyword order

3. Given the view creation:
CREATE VIEW ActiveUsers AS SELECT id, name FROM Users WHERE active = 1;
What will the query SELECT * FROM ActiveUsers; return?

medium

A. Only users with active = 1

B. Only user IDs without names

C. An error because views cannot filter data

D. All users including inactive ones

Solution

1. Step 1: Understand the view definition

   The view selects id and name from Users where active = 1, so only active users are included.

2. Step 2: Analyze the SELECT from the view

   Selecting * from ActiveUsers returns all columns defined in the view, filtered by active = 1.

3. Final Answer:

   Only users with active = 1 -> Option A

4. Quick Check:

   View filters rows = active users only [OK]

Hint: View returns filtered rows as defined in SELECT [OK]

Common Mistakes:

• Assuming view returns all table rows
• Thinking views cannot filter data
• Expecting columns not in view to appear

4. Identify the error in this view creation statement:
CREATE VIEW SalesView SELECT * FROM Sales;

medium

A. SELECT * is not allowed in views

B. View name cannot be SalesView

C. Missing AS keyword before SELECT

D. CREATE VIEW must include WHERE clause

Solution

1. Step 1: Check the syntax of CREATE VIEW

   The correct syntax requires AS before the SELECT statement.

2. Step 2: Identify the missing keyword

   The statement misses AS, causing a syntax error.

3. Final Answer:

   Missing AS keyword before SELECT -> Option C

4. Quick Check:

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

Hint: Always include AS before SELECT in CREATE VIEW [OK]

Common Mistakes:

• Omitting AS keyword
• Misplacing SELECT clause
• Assuming WHERE clause is mandatory

5. You want to create a view TopProducts that shows product names and total sales only for products with sales over 1000. Which SQL statement correctly creates this view?

hard

A. CREATE VIEW TopProducts AS SELECT product_name, sales FROM Products WHERE sales > 1000;

B. CREATE VIEW TopProducts AS SELECT product_name, SUM(sales) FROM Products GROUP BY product_name WHERE SUM(sales) > 1000;

C. CREATE VIEW TopProducts AS SELECT product_name, SUM(sales) FROM Products WHERE SUM(sales) > 1000 GROUP BY product_name;

D. CREATE VIEW TopProducts AS SELECT product_name, SUM(sales) FROM Products GROUP BY product_name HAVING SUM(sales) > 1000;

Solution

1. Step 1: Understand the requirement

   We need product names and total sales, only for products with total sales over 1000.

2. Step 2: Use GROUP BY and HAVING correctly

   SUM(sales) requires GROUP BY product_name, and filtering on aggregated values uses HAVING.

3. Step 3: Check each option

   CREATE VIEW TopProducts AS SELECT product_name, SUM(sales) FROM Products GROUP BY product_name HAVING SUM(sales) > 1000; uses GROUP BY and HAVING correctly; others misuse WHERE or clause order.

4. Final Answer:

   CREATE VIEW TopProducts AS SELECT product_name, SUM(sales) FROM Products GROUP BY product_name HAVING SUM(sales) > 1000; -> Option D

5. Quick Check:

   Use HAVING for aggregated filters in views [OK]

Hint: Use HAVING for conditions on aggregates in views [OK]

Common Mistakes:

• Using WHERE with aggregate functions
• Placing WHERE after GROUP BY
• Omitting GROUP BY when using SUM