Replacing NULL values
You are interested in knowing what companies US customers work for. Not all customers have provided the company they work for at the moment they signed up at eSymphony. This means there are some NULL values in the data. You want any eSymphony employees that look at your query later on to understand the result. This is why you decide to add a No affiliation tag to customers that haven't completed the Company field.
There are two functions, both introduced in the video, that you can use to achieve this.
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Introduction to Oracle SQL
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-- Replace NULL values in the Company field
SELECT ___ AS Affiliation, COUNT(*)
FROM Customer
-- Filter on the country USA
___
-- Group by company
GROUP BY ___