New Microsoft SQL Server Video Tutorial: When to Use HAVING Instead of WHERE - Aggregates, GROUP BY, and the HAVING Clause

When to Use HAVING Instead of WHERE - Aggregates, GROUP BY, and the HAVING Clause - view details

The traditional areas of difficulty for SQL developers are aggregates, JOINs, and subqueries. Most people have no trouble understanding when to use COUNT instead of SUM but they get "stuck" when it comes to determining how to filter the data. Suppose you are asked to find all orders in 2006 in which customers ordered more than 5 items - how would you solve this query? Obviously you need two filters: for the date (2006) and for orders with more than 5 items. People have difficulty with this type of query however; most people would approach this query along these lines: "SELECT ... FROM Orders JOIN OrderDetails ... WHERE Year(DateOrdered)=2006 AND COUNT(*) > 5". Fo cus on the WHERE clause for a moment: is that right? If you aren't sure or if you think it is right, then you need to watch this video to understanding why this query must use the HAVING clause.

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• Source: SQL Server videos
• Category: Transact-SQL Basics: Queries, Stored Procedures, Functions and more
• Skill Level: 300 (Intermediate)
• Length: 11:12 (8.37MB)
• Applies to Versions: SQL Server - All Versions
• Full Details

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Keywords Associated with this video: having, aggregates where clause, group by