I have a local repo for development and a production server in Laravel.
When I work locally, as the project grows, so does the DB. Therefore I keep adding new migrations that sometimes change existing tables. Locally I can refresh / recreate tables and seed without worrying.
However when I want to update the production DB where actual data is stored, what's the best method? If I need to update an existing table I cannot just drop and recreate it, as data would be lost. And if I run the migration directly, I get an error like "table already exists". So I end up manually adding the fields in the DB, which I don't think it's the best way to go.
As already mentioned, you can create migrations to update the columns without dropping the tables. And the 'Modifying columns' docs provide a clear explanation for this. However that is docs for modifying columns, if you want to modify tables instead of columns, you can use the 'Updating tables' docs
This uses the SchemaBuilder to do various things, for example, adding columns in an existing table:
Schema::table('table_name'), function ($table) {
$table->string('new_column')->after('existing_column');
// however you can leave the ->after() part out, this just specifies that the
// new column should be insterted after the specified column.
});
Or delete a column from an existing table
Schema::table('table_name'), function ($table) {
$table->dropColumn('new_column');
});
You can also rename but I'll leave it to you to explore the docs further.
Related
i'd like to know if it's possible at all to update the table schema in a Migration through a specific Eloquent Model, or if i actually need to pass in the name of the Table and Connection every single time.
I ask this because in my case this requires an additional configuration file that my package must publish to the end users, apart from the already required table Eloquent model (which is used for other purposes)
You can update schema later and add or drop columns and/or index.
To do this you create a new migration and add the changes there. It will change the table over your previous version.
More info in Laravel documentation.
For renaming the table
Schema::rename($from, $to);
https://laravel.com/docs/5.2/migrations#renaming-and-dropping-tables
Im working on an online store project where I have already made it possible for an administrator to update different table entries via the store gui (like items, user profiles, orders etc). SaveChanges(); is used to save the changes.
Im currently trying to figure out how to make this work:
An entry in table "items" gets updated.
Before the entry in the table "items" gets updated, a copy of the old entry gets saved into a table named "history-items".
The copy that is saved to "history-items" preferably has a timestamp.
How would I go about doing this? (As you might tell, I just recently picked up visual studio, and am pretty new to everything)
Thank you.
There are atleast 3 ways to do this:
If you are using SQL Server 2008 or newer this is now built in functionality, see: http://msdn.microsoft.com/en-us/library/bb933994.aspx
If you opt not to use that then the simplest solution is to use database triggers.
If you want to do it in C# code, then you need to read the original values before saving, and save these original values to the history table. For reading original values see: How to get original values of an entity in Entity Framework?
I would go for option 1 if possible.
I am very new to EF programming.
My application gets the data from existing database. (DB first)
Now I have come to situation where I want to update my model to newer DB. basically the core schema is same as previous but has some modification in the table.
When I change the DB name for app.config and update the model it gives list of error
have I missed something?
When you do an update it merges the model you have with the DB that you update from. Additional columns are added to your existing entities but columns that you have removed from the DB are not removed from your entities and you need to remove these mappings yourself.
If you know which tables have columns removed it sometimes easier to delete the entity from your model and then do an update to reload it from the DB.
If you've don't know what tables or there have been many then it may be easier to delete all entities from your model and just do a full Update to reload the the new DB structure.
I have uploaded my MVC3 project , it's s simple blog , at first it works well but after couple hours! following error appears (I've made custom error to Off to see the error)
The model backing the 'SiteContext' context has changed since the database was created. Either manually delete/update the database, or call Database.SetInitializer with an IDatabaseInitializer instance. For example, the DropCreateDatabaseIfModelChanges strategy will automatically delete and recreate the database, and optionally seed it with new data.
to solve this I have to manually delete my database and create again and then restore to the backup that I have created. but after after 2 hours again I get the error!
I really don't have any idea , what caused that ??
When you create a model and ask EF to create a database from it, EF would hash the model and store the hash value with the database. Whenever the context is created, EF recomputes the hash and matches it against what is stored at the database. If the model changes in any way, the resulting hash will be different and EF will throw the exception you have just seen. This is done in order to keep the model in sync with the database.
Is there any way the model could have changed during runtime?
One thing you could do to figure out the difference is to
1.Re-create the database from the model as you are doing now and get it scripted (script1.sql).
2.Wait till the error happens and delete the db and re-create it again and script it (script2.sql)
3.Try to compare the two and see whether you can spot a difference in the schemas.
This should give you an idea of what has changed in the model.
Goodluck
I have an existing MVC3 application and database that is on a SQL Server 2008 R2 and I had to add a bool item to an existing model.
After I added it to the model, I rebuilt and published the project. Then I opened up SQL Server Management Studio and went to the table and added the entry to the column as a bit, I had to make it nullable since the table already contains data.
I thought this would be all that I would need to do to get everything working. However I got this error:
The model backing the 'psllc_DB' context has changed since the database was created. Either manually delete/update the database, or call Database.SetInitializer with an IDatabaseInitializer instance. For example, the DropCreateDatabaseIfModelChanges strategy will automatically delete and recreate the database, and optionally seed it with new data.
I'm not sure what else to do, I went back to the code and changed the bool to bool? so it will be nullable but this didn't help either. I can't drop the entire database since it's full of data, however as a last ditch possibility I could drop this table and re-create it cause it only has a few entries, but I don't know if that will work. I'm not sure what else to do so any advice would be very appreciated.
Update
Since I'm not getting any responses, let me rephrase my question.
How should I update my database (a SQL Express mdf file) to add a bool Column to a Table that has data already? I need the database to match my updated MVC 3 Entity Code First model otherwise I get the above error.
Thanks
Since this is code-first, you should do this code-first: change the class and use EF-migrations to change the database. The way you do it, the model and the database may match, but the meta information in the database is not updated.
By the way, if you supply a default value, you can add a non-nullable column.