daohualiuxiang
/
AspNetCore.Docs
mirror of https://github.com/dotnet/AspNetCore.Docs.git
1
0
Fork 0
Code Issues Packages Projects Releases Wiki Activity

Moved section earlier in this tutorial (#9063) 

A link to the FK section is actually provided, but it is easy to gloss over. Moving the section up in the document prevents users reading it too late to do anything about it, as said in the issue.

Fixes #7728
pull/9105/head
Dave Brock 2018-10-18 13:19:38 -05:00 committed by Rick Anderson
parent 8038921da3
commit 5509a97557
1 changed files with 13 additions and 8 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

21
aspnetcore/data/ef-rp/complex-data-model.md
View File

@ -571,10 +571,15 @@ The ALTER TABLE statement conflicted with the FOREIGN KEY constraint "FK_dbo.Cou
database "ContosoUniversity", table "dbo.Department", column 'DepartmentID'.
```
When migrations are run with existing data, there may be FK constraints that are not satisfied with the exiting data. For this tutorial, a new DB is created, so there are no FK constraint violations. See
[Fixing foreign key constraints with legacy data](#fk) for instructions on how to fix the FK violations on the current DB.
## Apply the migration
### Drop and update the database
Now that you have an existing database, you need to think about how to apply future changes to it. This tutorial shows two approaches:
* [Drop and re-create the database](#drop)
* [Apply the migration to the existing database](#applyexisting). While this method is more complex and time-consuming, it's the preferred approach for real-world, production environments. **Note**: This is an optional section of the tutorial. You can do the drop and re-create steps and skip this section. If you do want to follow the steps in this section, don't do the drop and re-create steps.
<a name="drop"></a>
### Drop and re-create the database
The code in the updated `DbInitializer` adds seed data for the new entities. To force EF Core to create a new DB, drop and update the DB:
@ -618,13 +623,13 @@ Examine the **CourseAssignment** table:
![CourseAssignment data in SSOX](complex-data-model/_static/ssox-ci-data.png)
<a name="fk"></a>
<a name="applyexisting"></a>
## Fixing foreign key constraints with legacy data
### Apply the migration to the existing database
This section is optional.
This section is optional. These steps work only if you skipped the preceding [Drop and re-create the database](#drop) section.
When migrations are run with existing data, there may be FK constraints that are not satisfied with the exiting data. With production data, steps must be taken to migrate the existing data. This section provides an example of fixing FK constraint violations. Don't make these code changes without a backup. Don't make these code changes if you completed the previous section and updated the database.
When migrations are run with existing data, there may be FK constraints that are not satisfied with the existing data. With production data, steps must be taken to migrate the existing data. This section provides an example of fixing FK constraint violations. Don't make these code changes without a backup. Don't make these code changes if you completed the previous section and updated the database.
The *{timestamp}_ComplexDataModel.cs* file contains the following code:
@ -637,7 +642,7 @@ To make the `ComplexDataModel` migration work with existing data:
* Change the code to give the new column (`DepartmentID`) a default value.
* Create a fake department named "Temp" to act as the default department.
### Fix the foreign key constraints
#### Fix the foreign key constraints
Update the `ComplexDataModel` classes `Up` method: