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Easily Integrate with Any RESTful API Using the CData API Driver

The evolution of APIs has opened up exciting opportunities for businesses. RESTful APIs are a consistent, straightforward way that enables businesses to work with external data and offer access to their own data. In May 2021, the number of public APIs grew beyond 24,000, with about 2,000 APIs added just since 2019.  APIs continue to be beneficial to businesses and developers, and with the CData API Driver, it […]

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2021-11-15

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Question of the Day

Using Outer Joins

I have this data in a SQL Server 2019 database:

Customer table
CustomerID CustomerName
1          Steve
2          Andy
3          Brian
4          Allen
5          Devin
6          Sally

OrderHeader table
OrderID CustomerID OrderDate
1       1          2024-02-01
2       1          2024-03-01
3       3          2024-04-01
4       4          2024-05-01
6       4          2024-05-01
7       3          2024-06-07
8       2          2024-04-07
I want a list of all customers and their order counts for a period of time, including zero orders. If I run this query, how many rows are returned?
SELECT 
  c.CustomerName, COUNT(oh.OrderID)
 FROM dbo.Customer AS c
LEFT JOIN dbo.OrderHeader AS oh ON oh.CustomerID = c.CustomerID
WHERE oh.Orderdate > '2024/04/01'
GROUP BY c.CustomerName

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