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Suppose you have a PostgreSQL database that contains three tables, orders, order_details and customers. The orders table contains basic information about each order, including the order ID and customer ID, customers table contains information about customer, while the order_details table contains the details of each order, including the product ID, quantity, and price. You want to create a view that shows the order ID, customer name, product name, quantity, and price for all orders.

Example of the orders table:

order_id	customer_id	order_date
1	1	2022-03-01
2	2	2022-03-02
3	1	2022-03-03
4	3	2022-03-04

Example of the order_details table:

order_id	product_id	quantity	price
1	1	3	10.00
2	2	5	15.00
1	3	2	20.00
4	1	1	8.50

Example of the customers table:

customer_id	customer_name	city
1	Laurence Lebihan	London
2	Diego Roel	Madrid

Which of the following CREATE VIEW statements would accomplish this?

CREATE VIEW order_details_view AS

SELECT o.order_id, c.customer_name, d.product_name, d.quantity, d.price

FROM orders o

JOIN order_details d ON o.order_id = d.order_id

JOIN customers c ON o.customer_id = c.customer_id;

✅

CREATE VIEW order_details_view AS

SELECT order_id, customer_name, product_name, quantity, price

FROM orders

JOIN order_details ON orders.order_id = order_details.order_id

JOIN customers ON orders.customer_id = customers.customer_id;

❌

CREATE VIEW order_details_view AS

SELECT order_id, customer_name, product_name, quantity, price

FROM orders

INNER JOIN order_details ON orders.order_id = order_details.order_id

INNER JOIN customers ON orders.customer_id = customers.customer_id;

❌

CREATE VIEW order_details_view AS

SELECT o.order_id, c.customer_name, d.product_name, d.quantity, d.price

FROM orders o, order_details d, customers c

WHERE o.order_id = d.order_id

AND o.customer_id = c.customer_id;

✅

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Suppose you have two tables in a PostgreSQL database, orders and products. You want to create a view that shows the order ID, product name, and quantity for all orders that include a particular product. Which of the following CREATE VIEW statements would accomplish this?

Table Example:

orders table:

| order_id | product_id | quantity |

|----------|------------|----------|

| 1 | 1 | 3 |

| 2 | 2 | 5 |

| 3 | 1 | 2 |

| 4 | 3 | 1 |

products table:

| id | product_name |

|----|--------------|

| 1 | Widget A |

| 2 | Widget B |

| 3 | Widget C |

CREATE VIEW order_product AS

SELECT order_id, product_name, quantity

FROM orders

JOIN products ON orders.product_id = products.id

WHERE product_name = 'example_product';

✅

CREATE VIEW order_product AS

SELECT orders.order_id, products.product_name, orders.quantity

FROM orders, products

WHERE orders.product_id = products.id

AND products.product_name = 'example_product';

✅

CREATE VIEW order_product AS

SELECT orders.order_id, products.product_name, orders.quantity

FROM orders, products

WHERE orders.product_id = products.id

AND products.product_name LIKE '%example_product%';

❌

CREATE VIEW order_product AS

SELECT order_id, product_name, quantity

FROM orders

JOIN products ON orders.product_id = products.id

HAVING product_name = 'example_product';

❌

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What is the difference between a regular view and a materialized view in PostgreSQL?

Regular views are read-only, while materialized views allow data modification

❌

Materialized views are not updated automatically when underlying data changes, while regular views always reflect real-time data

✅

There is no difference; both terms are used interchangeably in PostgreSQL

❌

Regular views store data physically on disk, while materialized views are virtual

❌

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What is the benefit of using materialized (indexed) views?

They can materialize (persist) the the results of view in a table-like form

✅

They can help to simplify complex queries and join data from multiple tables

❌

They can combine data from one or more base tables (or views) into a new virtual table

❌

They can join horizontally partitioned data from one or more base tables across one or more servers

❌

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Which type of view combines data from one or more base tables (or views) into a new virtual table?

Partitioned views

Indexed views

Logical views

Standard views

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What is a SQL View?

A group of related tables that are linked together

❌

A query that retrieves and displays data from one or more tables

✅

A stored procedure that performs a set of operations on data

❌

A physical table that stores data

❌

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What is the correct syntax for deleting records from table_name with a specific condition in PostgreSQL?

DELETE WHERE condition SET column = value;

❌

DELETE FROM table_name WHERE condition;

✅

DELETE WHERE condition from table_name;

❌

DELETE SET column = value WHERE condition;

❌

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Suppose you have a table named sales with columns id, product_name, quantity, and price. You want to update the column total_price by multiplying the quantity and price columns. Which SQL statement will achieve this?

UPDATE FROM sales SET total_price = (quantity * price);

❌

UPDATE TABLE sales SET total_price = quantity * price;

❌

UPDATE sales SET total_price = quantity - price;

❌

UPDATE sales SET total_price = quantity * price;

✅

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How can you insert the result of a SELECT query with a GROUP BY clause and an ORDER BY the sum in descending order into a new table in PostgreSQL?

INSERT INTO new_table (column1, column2, total)

SELECT column1, column2, SUM(column3) AS total

FROM original_table

GROUP BY column1, column2

ORDER BY total DESC;

✅

INSERT INTO new_table

SELECT column1, column2, SUM(column3)

FROM original_table

GROUP BY column1, column2

ORDER BY column3 ASC;

INSERT INTO new_table

SELECT column1, column2, SUM(column3)

FROM original_table

GROUP BY column1, column2

ORDER BY column3 DESC;

INSERT INTO new_table

SELECT column1, column2, AVG(column3)

FROM original_table

GROUP BY column1, column2

ORDER BY column3 ASC;

INSERT INTO new_table (column1, column2, total)

SELECT column1, column2, SUM(column3)

FROM original_table

GROUP BY column1, column2

ORDER BY SUM(column3) DESC;

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How to insert records into a table using a nested subquery and the ANY operator in PostgreSQL?

INSERT INTO table1 (col1, col2)

SELECT col1, col2

FROM table2

WHERE col3 NOT ANY (SELECT col3 FROM table3);

❌

INSERT INTO table1 (col1, col2)

SELECT col1, col2

FROM table2

WHERE col3 IN (SELECT col3 FROM table3);

❌

INSERT INTO table1 (col1, col2)

SELECT col1, col2

FROM table2

WHERE col3 = (SELECT col3 FROM table3);

❌

INSERT INTO table1 (col1, col2)

SELECT col1, col2

FROM table2

WHERE col3 = ANY (SELECT col3 FROM table3);

✅

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