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could anyone help me answer this question:
Describe transactions and explain the main principles.
I think this link might be helpful
http://www.tutorialspoint.com/sqlite/sqlite_transactions.htm
There are many reasons for them. Among other reasons, transactions protect the integrity of your database data by allowing you to decide at the end of a session whether you want to commit the changes or revert back to the state the database was before you started making changes. Cases where you would want to revert back might be cases where an error occurs in your program while.
For example, if you are building a program for a bank that handles money transfers, you will likely make a query to update the balance in the customer's first account to be what it was minus the transfer amount. However, if you run into an error when attempting to update the second account, it would be nice to just abandon all the changes made and return both tables to their original state.
I hope the link helps.
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I'm designing quite simple database for storing the hotel rooms reservations. The Reservation object in the database has StartDate, EndDate, RoomId, and ClienId fields. The most frequent query to the database will be to retrieve reservations for certain period of time (e.g. find all reservations in December 2024). So, with time I assume that there will be quite alot of reservations (maybe 10000-25000), and of course I can just delete old reservations, but theoretically, is it possible for the database to swiftly execute this query in such a big data? As I understand, database will automatically organise all reservations by StartDate. Am I right? Should I even wary about that, or all modern databases will do all this "dirty work" for me? What articles/books can you recommend for me to read about databases performance?
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Anyone cleared Snowflake's SnowPro Certification? I need help with and information about what did you do in order to prepare for this certification. I appreciate your information.
Thank you,
Prashanth.
Snowflake did officially launch the SnowPro Core Certification publicly on Tuesday, October 29th.
To view more information about the SnowPro Core Certification, you can navigate to https://community.snowflake.com/s/snowprocertifications.
No. They dont have transparent process for certification.
First, They have only online proctoring exam, they wont even give option to choose test center on your own.
But when you start the online exam by agreeing to all their conditions (arranging external usb camera, high speed internet etc) they will suspend or stop it by giving some silly reason and tell you to choose test centre by paying $100 more.
Later when you question back they will edit the requirement document itself and tell you are not meeting the requirements. (PFA sample of their requirement change)
Funny thing is they dont even know where is their Server.
It is one of the rubbish process I have seen, Please dont take up this certification and get trapped like me.
Portland OR is mentioned
Phoenix Arizona is mentioned later
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I want to use multithread to write data to MSSQL database in C++. Can I do it?
I think It can deadlocked or we must to wait. But I still want use multithread. Any idea?
Can I do it?
Can you program or are you willing to learn it? Because the "I" in the question is the critical thing. What you ask for is technically possible - but I have no idea whether you are capable of it.
I think It can deadlocked or we must to wait.
Generally every multi threaded data access MAY deadlock or wait. Which includes multi machine access - i.e. have hundreds of users accessing one database. Is there a question in there? The approaches to avoid deadlocks are well documented. Wait (i.e. wait for a writable lock) is also well documented.
But I still want use multithread. Any idea?
Learn enough programming to "just do it". Because this really is it - just do it.
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I'm trying to figure out if http://docs.phonegap.com/en/1.2.0/phonegap_storage_storage.md.html can handle versioning, conflicts, etc. similar to CouchDB's capabilities.
I'm building a mobile app wherein friends can share data. This data will be manipulated (add, edit, delete) when the app is online or offline. During offline operations, the data changes will be stored locally -- and then sync to a central database when it goes online (and everyone else will sync to that central database).
Obviously, there will be versioning, conflicts, etc. issues. CouchDB supposedly handles this well. However, I want to know if PhoneGap's storage is sufficient for my needs. Will it work or not?
sqlite has plenty of power for this kinda stuff, though even localstorage is pretty powerful unless you are manipulating data with heavy javascript. I say try localstorage first as it's very very easy to handle.
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Is it a good practice to check for database changes to have took place, or is it just a statistically irrelevant overkill?
Ex: user updates some data. JavaScript sends the new data to the server and displays that changes have took place in the callback. Should the server check that the updated record (or node or whatever) has in fact the updated value (selecting it and comparing it with the POST data), or is this just a waste of resources?
My best guess is that you're asking if your code should confirm that a database update actually happened.
Client writes data to database.
Updated data gets sent back to the client.
Double checking that the operation was successful by comparing the POST and the data in the database.
You don't need to do step 3. It's redundant and as you are guessing, it's more work for the server and database.
Once you write the code and test it, you can trust it's ok. No need to double check.