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Brush Up Your SQL

Thanks to LINQ and Entity Framework, I don't write a lot of online, transactional SQL any more (I like to think that, thanks to Entity Framework, I have Microsoft's ADO.NET team doing that for me). But there are features in SQL that just aren't available in the current version of LINQ (see my columns on SQL Server 2016's support for JSON and temporal tables for examples).

But it isn't just new features that may drive you to issuing raw SQL through Entity Framework, though.

For example, I had someone attending one of the SQL Server querying classes I teach with a problem that LINQ couldn't solve efficiently (I also teach the 2014 course, though it doesn't really matter because they're exactly the same course ... though, as I remember, the 2016 certification exam was easier).

His problem was that he was receiving a constant stream of reports from various vehicles and needed, from that received data to determine when the vehicle had stopped to refuel. The only way to answer this question is to compare the amount of gas in the tank at (time A) with the amount in the tank at (time A – 5 minutes).

In LINQ, this could be solved by joining every report row with all the report row from the same vehicle more than 5 minutes ago ... but that query had a response time that could be measured with a calendar, not with a stop watch. However, a raw SQL query that used the Preceding keyword (not available in LINQ), gave a very snappy response.

I love LINQ. I love Entity Framework. You're still going to need SQL.

Posted by Peter Vogel on 03/05/2018 at 7:20 AM


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