Andy Warren

I'm Andy Warren, currently a SQL Server trainer with End to End Training. Over the past few years I've been a developer, DBA, and IT Director. I was one of the original founders of SQLServerCentral.com and helped grow that community from zero to about 300k members before deciding to move on to other ventures.

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Blog Post

Schema & Renaming Fun

I wrote the SQLServerCentral question of the day that is live today called Schema & Renaming Fun. Mildly interesting, but looking...

2014-03-12

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Blogs

Taming Database Challenges: Insights from Redgate Keynote

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I am excited to cover the Microsoft Keynote on Day 2: Redgate Keynote: Simplifying...

AI Innovation in Microsoft Keynote

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I’m thrilled to be covering the Microsoft Keynote: Fuel AI Innovation with Azure Databases on Day...

Benefits of Migrating from Azure Synapse Analytics to Microsoft Fabric

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Many customers ask me about the advantages of moving from Azure Synapse Analytics to...

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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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