I'm having a lot of trouble with a DB first approach to an oracle database. Most of the time when I try to update the model my update-wizard crashes. I'm pretty sure this has to do with ODP.net .
the DBA just added a column to the database and a few hours ago I was able to update my model from the database, but i had a few minor issues (one column was renamed etc..) So I decided to undo pending changes on my entire Solution and start over.
I've been trying a whole lot of stuff the last few hours to just update the model again but It has come to a point that my update-wizard constantly crashes when I perform a refresh of my tables.
I can't work like this anymore. Is there a way to convert my edmx file to a code first approach so that I don't need to perform this refresh anymore?
Much appreciated if anyone can guide me in the right direction here...
Related
Recently I came across an interesting problem. Basically I have a database of schools which manages records of teachers, students, parents etc.
Theory:
Now, with every changing school session I want to be able to update the information of (say) student's class while maintaining the old information as well. One solution to this I thought would be to create a new instance of mongodb database thats would be the exact copy of the original one that runs on the same server, so I'll have 2 instances of the same database (one that has data of current school session and one that has the data of last year's session) running on same server.
Now I can query a specific instance based on my needs and get the appropriate data. Any changes would be done on the current school session while the old one would be treated as historical data.
Application:
Now I can't exactly figure out how to do it. I've looked into mongodb database versioning but even that doesn't seems to do it. One thing I know I don't want to do is to create an extra field on each of the collection's schema named version and manipulate it somehow which most of the solutions seems to suggest. I know mongodb has and __v field but I don't think that would be very useful (I could be wrong).
Any help is appreciated, Thanks
I have a mongoDb database with one of the collection having 2300000 documents and growing. Till the database had 1000000 documents the api response time was quick and the webpage loaded quickly, as soon as it crossed the 2000000 mark it started giving issues and took about a 100 seconds to find and throw the data. I dont know what to do with this sudden surge in the data, are there any practices that I have to follow inorder to manage and reduce the response time from the APIs
The data that im trying to fetch is based on date and the query has to run through the entire database inorder to find data for just one day.
I searched for a lot of things but am not able to find the solution.
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Index is probably the solution for you.
Can you provide example of both a typical document and the query you run?
Are you retrieving (or do you really need) the whole documents, or just some fields on them?
Typically i would suggest to create an index on your date field, with inverse order, it will surely improve your search if it concerns the more recent documents. I can help you to achieve it if you need.
This doc will help you to understand indexes and how to optimize queries.
I am wondering about the model-first approach. I wish to design a new database using the model designer in VS2012. The new features of the model designer such as coloring and splitting up model sections are wonderful. Hopefully there will be purpose for using the model designer beyond initially creating a new database.
I would like to perform the following steps...
using the model designer, visually design and push the model to create the initial database and a table
add data to the table
make a change to the table in the model designer (e.g. add a field)
push the changes to the database (i.e. update the database)
NOT LOSE MY DATA FROM STEP 2. Also, just to clear any confusion... did I mention that I DON'T WISH TO LOSE THE DATA?
Please, please tell me this obvious need (i.e. the need to evolve the the tables and their fields without losing data, starting from scratch) has not been overlooked in iteration FIVE of EF.
This page on EF (http://msdn.microsoft.com/en-us/data/ee712907.aspx) makes things sound that the developer has equal choices between coding first and modeling first. To me, the intro video on the page creates a similar impression.
It would be nice if there were a simple menu option or better yet just a way to establish "automatic pushes to DB" upon changes to the model. That way whenever changes are made and the SAVE button is clicked, a dialog could appear "Update database?".
I see that using code-first there is a migrations option. I cannot seem to find the same for model-first. And I don't understand why this wouldn't be possible... after all the code that I would have written in code-first does indeed exist - it was created by the model-first code generation.
I'm keeping my fingers crossed in hopes someone will have a simple solution, perhaps something I've just overlooked and all this rambling/venting is in vain. :-)
You really have to use code-first if you want to modify your database when the model changes. Even then it's not some magical automated process but you'll have to script the changes.
With model first your best option is to generate a new database each time and create a change script (DDL) by using a tool like Redgate's SQL Compare or a Visual Studio Sql Server Database Project.
I'd like to add that it is virtually impossible to synchronize a database automatically with a model. Some changes require manual intervention, e.g. removing a field and adding another field cannot be distinguished from renaming/retyping a field. Some changed can easily be done in a model, but would require a table rebuild script in Sql Server (e.g. changing field order), or a combination of modified content and structure (e.g. making a field not null, adding a foreign key).
At the moment the only thing to do is:
Copy your database file... (backup)
Allow EF to recreate the database according to model
Per table copy-paste your records from backup to your new db.
This is not that easy as you need to copy paste in a specific order because of relations and it will only be good for minor changes such as adding columns and new tables or removing scalar columns or removing tables.
But I am certain that this is the begining of a correct approach to deal with the problem which later on can be automated by writing a more generic migration app between two databases which share same table names and relations.
Deeper problems begin when the relations are not the same / table names changed / column names changed.
A little background to my question. I work for a company that is charged with retrieving data from databases from all 50 states and DC. I take this data and reformat it in excel. Once it's reformatted I use SQL Server to upload it to our website vetportal.agdata.net. While some states are not so bad, retrieving information from others make it very painful to sort through.
I have 2 questions:
Can a code be written so that a new database can be crossed checked with the old database (our records) and update the information in the old database while also excluding duplicate information?
Can a code be written to take a number from an open excel sheet, switch over to an open website, input the number, search for the individual, and extract his/her information, and finally update the excel with that information then move on to the next person? Ex, WA State's website is set up so that you can only look up one person at a time which is very tedious when going through 1200+ individuals.
I have some experience with C++ and have written programs that draw code from other files, but mainly only equations or values which then get evaluated in my code so I know this is a bit different.
I guess if you have a repetitive technological problem you can solve it with some programming.
Your questions:
You can make that with a little app, that using SQL reads the information from the new database and checks/updates the information of the old database.
This code is a little more difficult to do, but i guess it can be done. In C++, I don't know if there is any library that can already open Excel files, but in Java you have the Apache POI, that way you can open your excel file in the application, then while iterating through the information you open the website in the application, and submit the form you want with your number, getting the response and parsing it.
If you want to make this in Java I think it will not waste you too much time if you know C++ . The only exception is opening the website in java and parsing it which will take more time to learn and do.
Hope it helps!
1) Yes. Depending on the databases, you may be able to do a db to db connection. You could then write a query using an INNER JOIN to update information in the old database and exclude duplicates.
2) A few ways to approach this problem. Depending on your language (mine is PHP) you could use an open source class such as PHPExcel to open the sheet and fetch & update website data (cURL). You could also write some VBA within Excel that could do similar functionality.
I'm in a VERY difficult problem.
I have a Microsoft Access Data Base, but it was made in the most chaotic way possible. The DB has like 150+ tables, Only uses like 50% of the tables. The relations are almost random. But, somehow, it delivers some information.
I need to get a particular component of the DB, but is so tangled that I can not manage to get into the table that creates that value. I revised every table, one by one, and found nothing.
I used mdbtools for Linux to try to inspect with more details the DB. But unfortunately has not been developed in years, and it closes every time. Maybe because the DB is "big" ? -700 mg-
I'm wondering: is there a way to see all the relations the arrives to the particular value I'm looking? Or to decompile the DB? I have no idea in which language it was made. I'm suspecting that it was made in Visual, just because is rather crappy.
Well, waiting for some help.
I would suggest using (still) MS Access for this. But, if relationships look messy on the diagram, you can query one of the system tables (MSysRelationships) directly to get ALL the relationships you need (e.g. for particular table etc.):
To unhide system tables in early versions of Access (97-2003), follow the instructions here:
For Access 2007, do the following: