Sorting data using ORDER BY

Sorting data using the ORDER BY clause in SQL is a common operation that allows you to arrange query results in a specified order. Here are various types of sorting and real-time examples using the ORDER BY clause:

Ascending Order (ASC):
- Example: Retrieve a list of products sorted by their price in ascending order.
- SQL Query:
```
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SELECT * FROM Products ORDER BY price ASC;
```
- Explanation: This query sorts the products by their price column in ascending order, so the cheapest products appear first.
Descending Order (DESC):
- Example: Retrieve a list of customers sorted by their registration date in descending order.
- SQL Query:
```
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SELECT * FROM Customers ORDER BY registration_date DESC;
```
- Explanation: This query sorts the customers by their registration_date column in descending order, so the newest customers appear first.
Sorting by Multiple Columns:
- Example: Retrieve a list of orders sorted by customer ID in ascending order and then by order date in descending order.
- SQL Query:
```
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SELECT * FROM Orders ORDER BY customer_id ASC, order_date DESC;
```
- Explanation: This query first sorts the orders by customer_id in ascending order, and within each customer, it further sorts by order_date in descending order.
Sorting by Expressions:
- Example: Retrieve products sorted by their profit margin (calculated as selling_price - cost_price) in descending order.
- SQL Query:
```
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SELECT *, (selling_price - cost_price) AS profit_margin
FROM Products
ORDER BY profit_margin DESC;
```
- Explanation: This query calculates the profit margin for each product and sorts them in descending order based on the profit margin.
Sorting by Textual Columns:
- Example: Retrieve a list of employees sorted by their last names in ascending order.
- SQL Query:
```
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SELECT * FROM Employees ORDER BY last_name ASC;
```
- Explanation: This query sorts the employees by their last_name column in alphabetical order.
Sorting by Date and Time:
- Example: Retrieve a list of appointments sorted by appointment date and time in ascending order.
- SQL Query:
```
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SELECT * FROM Appointments ORDER BY appointment_datetime ASC;
```
- Explanation: This query sorts the appointments by their appointment_datetime column in chronological order.
Sorting with NULL Values:
- Example: Retrieve a list of products sorted by their availability date in ascending order, handling NULL values.
- SQL Query:
```
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SELECT * FROM Products ORDER BY availability_date ASC NULLS LAST;
```
- Explanation: This query sorts products by their availability_date in ascending order, placing NULL values at the end of the result set using NULLS LAST.
Sorting with LIMIT:
- Example: Retrieve the top 5 highest-priced products.
- SQL Query:
```
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SELECT * FROM Products ORDER BY price DESC LIMIT 5;
```
- Explanation: This query sorts products by price in descending order and limits the result to the top 5, giving you the highest-priced products.

These variations of the ORDER BY clause demonstrate how you can sort data in SQL queries to present it in a meaningful and organized way for various real-time scenarios.