I have a weird request as I support an application that does purging of historical data routinely which I would like to store in a separate datastore. I want to keep the schema of the database in the copy identical however I would like to be able to script a process which could take the changes to the primary database and replicate to the clone without deleting the data that the application is purging from the database tables.
How would I go about doing this?
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I am wondering what the best way (or any way) to manage a database schema. I have a sql file with a bunch of statements like CREATE TABLE Users { id SERIAL PRIMARY KEY ....}; which represents the schema for my database.
I have postgres installed on my dev machine however am having trouble syncing the changes I make to the schema with the local database. Currently I just run drop the entire database and run the schema file on the database.
I figure there has to be a better way I don't know about. I will also need to be able to set a database up for production when the project becomes more stabilized and obviously dropping a table in production wont work.
Suggestions?
I have a production and development database (on different systems of course). Many months ago, I copied the production database to the development system. I used exp/imp at the time. Since then there has been quite a few changes in the production database I would like to copy down to the development database. I'd rather not wipe out the development database and start over because of data I've had to add to the development database.
My original thought was to use MERGE INTO to copy the new records. But this apparently requires me to do this for tables, and list all fields of all tables. We're talking hundreds of tables and thousands of fields here. Not a pretty solution.
Is there an easier way?
Why not use the TABLE_EXISTS parameter of impdp to append the new data to the existing tables? Duplicate keys will error off but the rest of the data should still import. The results will be a bit messy. Prior to running TRUNCATE any tables in test where you can just bring the entire production table. Disable FK. Re-enable after import.
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Another option create a database link and generate INSERT/SELECT into all tables where data not in existing test table. You probably also want to disable FK prior to running and re-enable when done.
I've had an issue with a SQL Server database after an update from some horrible software. The software "updated" (in actuality, rolled-back) a bunch of encrypted stored procedures and user-defined functions in the database, which is now causing errors in other software.
Thankfully I took a backup from just before the update, however the error wasn't noticed until about an hour later which means records have been updated/inserted/deleted etc since the backup was taken.
Originally my idea was to simply copy the stored procedures and functions to a new database created from the backup, then backup and restore this database onto the broken database, but as they are encrypted I can't copy them.
So the next idea was to transfer the tables from the broken database to the restored database and proceed as above. However I run in to several issues with the existing tables, such as the DBTimeStamp column not allowing the copy. However copying the tables to new clean database works fine.
So here are the questions:
What's the best way to effectively merge the tables from the backup with the tables from the broken db?
Would simply truncating or dropping the existing tables in the backup avoid these validation errors? I get error messages like "VS_ISBROKEN" etc when trying to use the export data function to push the data across, with dropping the existing data set and Identity_Insert turned on etc. (Truncating)
I have yet to try dropping all the tables on the backup and going from there. Would there be an adverse effect with Metadata if I approached the problem this way?
I feel like this should be quite simple, and had the provider not locked down all the functions and stored procedures I wouldn't need to copy the tables out like this.
Thanks for reading :)
I am writing code to migrate data from our live Access database to a new Sql Server database which has a different schema with a reorganized structure. This Sql Server database will be used with a new version of our application in development.
I've been writing migrating code in C# that calls Sql Server and Access and transforms the data as required. I migrated for the first time a table which has entries related to new entries of another table that I have not updated recently, and that caused an error because the record in the corresponding table in SQL Server could not be found
So, my SqlServer productions table has data only up to 1/14/09, and I'm continuing to migrate more tables from Access. So I want to write an update method that can figure out what the new stuff is in Access that hasn't been reflected in Sql Server.
My current idea is to write a query on the SQL side which does SELECT Max(RunDate) FROM ProductionRuns, to give me the latest date in that field in the table. On the Access side, I would write a query that does SELECT * FROM ProductionRuns WHERE RunDate > ?, where the parameter is that max date found in SQL Server, and perform my translation step in code, and then insert the new data in Sql Server.
What I'm wondering is, do I have the syntax right for getting the latest date in that Sql Server table? And is there a better way to do this kind of migration of a live database?
Edit: What I've done is make a copy of the current live database. Which I can then migrate without worrying about changes, then use that to test during development, and then I can migrate the latest data whenever the new database and application go live.
I personally would divide the process into two steps.
I would create an exact copy of Access DB in SQLServer and copy all the data
Copy the data from this temporary SQLServer DB to your destination database
In that way you can write set of SQL code to accomplish second step task
Alternatively use SSIS
Generally when you convert data to a new database that will take it's place in porduction, you shut out all users of the database for a period of time, run the migration and turn on the new database. This ensures no changes to the data are made while doing the conversion. Of course I never would have done this using c# either. Data migration is a database task and should have been done in SSIS (or DTS if you have an older version of SQL Server).
If the databse you are converting to is just in development, I would create a backup of the Access database and load the data from there to test the data loading process and to get the data in so you can do the application development. Then when it is time to do the real load, you just close down the real database to users and use it to load from. If you are trying to keep both in synch wile you develop, well I wouldn't do that but if you must, make a nightly backup of the file and load first thing in the morning using your process.
You may want to look at investing in a tool like SQL Data Compare.
I believe it has support for access databases too, and you can download a trial.
I you are happy with you C# code, but it fails because of the constraints in your destination database you temporarily can disable them and then enable after you copy the whole lot.
I am assuming that your destination database is brand new DB with no data, and not used by anyone when the transfer happens
It sounds like you have two problems:
You're migrating data from one database to another.
You're changing your schema.
Doing either of these things is tricky if you are trying to migrate the data while people are using the data.
The simplest approach is to migrate the data based on a static copy of the data, and also to queue updates to that data from the moment you captured the static copy. I don't know how easy this is in Access, but in SQLServer or Oracle you can use the redo logs for this or a manual solution using triggers. The poor-man's way of doing this is to make triggers for all the relevant tables that log the primary key of the records that have changed. Then after the old database is shut off you can iterate over those keys and get those records from the old database and put them into the new database. Just copy the whole record; if the record was deleted then delete it from the new database.
Your problem is compounded by the fact that you can't simply copy the data, you have to transform it. This means you probably have to shut down both databases and re-migrate the records based on the change list. It will take a lot of planning to ensure you get things right and I'd recommend writing a testing script that can validate that the resulting data is correct.
Also I'd ensure that the code for the migration runs inside one of the databases if possible. Otherwise you are copying the data twice and this will significantly harm the performance.
I am developing an Adobe AIR application which stores data locally using a SQLite database.
At any time, I want the end user to synchronize his/her local data to a central MySQL database.
Any tips, advice for getting this right?
Performance and stability is the key (besides security ;))
I can think of a couple of ways:
Periodically, Dump your MySQL database and create a new SQLite database from the dump. You can then serve the SQLite database (SQLite databases are contained in a single file) for your users client to download and replace the current database.
Create a diff script that generates the necessary statements to bring the current database up to speed (various INSERT, UPDATE and DELETE statements). To do this, you must record the time of each change continuously in your database (the time of creation and update for each row, and keep a history of deleted rows).
User's client will download the diff file (a text file of the various statements) and apply it on the local database.
Both approaches have their own pros and cons - by dumping the entire database, you make sure all the data gets through. It is also much easier than creating the diff, however it might put more load on the server, depending on how often does the database gets updated between dumps.
On the other hand, diffing between the database will give you just the data that changed (hopefully), but it is more open to logical errors. It will incur an additional overhead on the client as well, since it will have to create/update all the necessary records instead of just copying a file.
If you're just sync'ing from the server to client, Eran's solution should work.
If you're just sync'ing from the client to the server, just reverse it.
If you're sync'ing both ways, have fun. You'll at minimum probably want to keep change logs, and you'll need to figure out how to deal with conflicts.