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Conditional DELETE and INSERT in PostgreSQL

Introduction We are comfortable with inserting/deleting record(s) into/from a table. But we sometimes get confused when we need to insert or delete records conditionally from a table. Let us look at an example. Example scenario Suppose we have a table, called ALL_EMPLOYEES, which contains all employees' information who are working or had ever worked for […]

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2021-06-18 (first published: )

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SQLServerCentral Article

Handling Row-level Errors in ADF Data Flows

If you are working with ADF (Azure Data Factory) data flows, then you may have noticed there was a new feature released in November 2020, which is useful to capture any error while inserting/updating the records in a SQL database. This article will describe how to setup the error row handling feature and why it's […]

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2021-06-16 (first published: )

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SQLServerCentral Article

Azure Storage: Blob and Data Lake Storage Gen2

Introduction Azure Storage is the service for storing different types of data. A storage account is created first. The storage account provides a unique namespace for different types of Azure storage data accessible from anywhere in the world over HTTP or HTTPS. Data in the Azure storage account is durable and highly available, secure, and […]

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2021-06-14 (first published: )

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Using Outer Joins

By Steve Jones - SSC Editor

Comments posted to this topic are about the item Using Outer Joins

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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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