If there are duplicate orders in the data, how do you count unique orders?

To count unique orders in data with duplicates, you need to use a method to remove duplicate records based on a key that uniquely identifies an order (for example, order_id). In SQL, this can be done using COUNT(DISTINCT order_id), and in Python with pandas — using the drop_duplicates() method or the nunique() function.

Example in SQL:

SELECT COUNT(DISTINCT order_id) AS unique_orders_count
FROM orders;

Example in Python with pandas:

import pandas as pd

df = pd.DataFrame({'order_id': [1, 2, 2, 3, 4, 4, 4]})
unique_orders = df['order_id'].nunique()
print(unique_orders)  # Will output 4