Asking for help, clarification, or responding to other answers. Once IOPS are exhausted, your query will take minutes to write on a big table. The best answers are voted up and rise to the top, Not the answer you're looking for? For further information on the topic see Non Updating Updates by Paul White. That portion could be added, but you would first need to show exactly where you are getting your dataset that you are merging into MyTable. Makes it easier to update because of the JOIN to the table you are updating. You have no compiler safety at all. It is up to the application to enquire and react. I'm in camp 2 - I want to prevent an update trigger. However, I have found that despite this, the EXISTS/EXCEPT method almost always performs better, even with very large workloads. It returns true if the column is in the list of values being updated. Still no dirty pages to be written, but a little more log activity. This is because of the need to then filter on all of those columns, and non-equality predicates are generally not able to use index seeks, and the overhead of table & index writes and transaction log entries as mentioned above. It will have three values - clean, dirty and deleted. Identify blue/translucent jelly-like animal on beach. It looks like I'm two years late to the game, here, but there is indeed a pretty lightweight way of doing what you're asking for. Complete Serialization. Why refined oil is cheaper than cold press oil? If there are triggers that take action on updates to the table they will fire even if nothing has changed, this could be a significant consideration if you have any complex triggers to consider. rev2023.5.1.43405. Here is a snippet from the stored proc script: Code Snippet I have provided my code sample below; Great if it can help someone else. Can I use an 11 watt LED bulb in a lamp rated for 8.6 watts maximum? Anyway, the result when SaveChanges is called is the following SQL: So you can clearly see, Entity Framework has not attempted to update any other fields - just the Dob field. Of course, there's always more than one way to bake a cake. In the real world, is your update statement really going to look like this: Because in the real world, tables have lots of columns. Compare the lines of code, performance implications, and semantic "feeling" of each, and pick the one that feels right. Built-in functions facilitate retrieval of changed values and management of tracking. This remains the case even where a non-clustered primary key exists on the heap. Site design / logo 2023 Stack Exchange Inc; user contributions licensed under CC BY-SA. It only takes a minute to sign up. If you don't know before hitting the data layer if there has been any change or not then you can do something like: This avoids any update if nothing has changed so it more efficient (the lookups needed to reject the update would be needed to perform it anyway and the extra CPU time for the comparison is vanishingly small unless you have huge data in any of the columns), but it is more work to maintain and more prone to errors so most of the time I would recommend keeping it simple and updating without checking every column, i.e.
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