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Dne 23.9.1938 byla vyhlášena mobilizace .

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technické vybavení(hardware)

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30-ti denní testování

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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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What is a commit in Git?

A file in the repository

A saved change to the repository

A way to undo changes in the repository

A branch in the repository

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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?

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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Which of the following cannot be stored in a relational database easily?

A set of product images

A list of customer names and emails

Customer purchase history

A table of sales transactions

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Which database feature ensures data is stored consistently (e.g., all customer emails follow the same format)?

Constraints

File folders

Handwritten records

Spreadsheets

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What is a common advantage of relational databases?

They reduce data redundancy (duplicate records)

They store only one type of data

They require manual searching

They make data retrieval slower

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