T sql duplicate key update

Python Pillow. Python Turtle. Verbal Ability. Interview Questions. Company Questions. Artificial Intelligence. Cloud Computing. Data Science. Angular 7. More importantly, performance aside, unless you both use an explicit transaction and elevate isolation level, multiple things could go wrong when the row doesn't already exist:.

That last one is the worst, IMHO, because it's the one that potentially corrupts data. But if you are lulled into a sense of security that the IF EXISTS check protects you from duplicates or key violations , that is a surprise waiting to happen. If you expect a column to act like a key, make it official and add a constraint.

I've fixed many deadlocks in my career by simply adjusting to the following pattern ditch the redundant check, wrap the sequence in a transaction, and protect the first table access with appropriate locking :. In the best case, if you are updating a row that already exists, it will be more efficient to only locate that row once. Combining this logic with the high-level operations that would have to happen in the database, it is slightly simpler:.

In this case, one path only incurs a single index operation. In both cases, the writer who won the race loses their data to anything the "loser" updated after them.

Note that overall throughput on a highly concurrent system might suffer, but that is a trade-off you should be willing to make. That you're getting lots of deadlock victims or key violation errors, but they're happening quickly, is not a good performance metric. Some folks would love to see all blocking removed from all scenarios, but some of that is blocking you absolutely want for data integrity.

Connect and share knowledge within a single location that is structured and easy to search. I sent the form and when the input is new I also create an empty hidden input field for the primary key column that's empty to add a new row to db.

Only this row is not being created. When user modifies existing row it does work. So the update on duplicate key part works, but the Insert part for a new field does not work. So that looks alright.

This is the form on the HTML side, and the jquery that adds the input and hidden field. This part works. I use brackets on the form field to create a posted array. Like said, when checking what gets posted it seems ok. Sorry for all the info, hopefully it makes sense, sorry for cumbersome method, but I really don't see why this doesn't work, although I suspect the problem lies in the db table settings or structure?

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