从EF6中的__migrationhistory表中删除数据后，如何在不丢失任何数据的情况下进行迁移？ [英] How do I take migration without losing any data after deleting data from __migrationhistory table in EF6?

问题描述

我不小心从__MigrationHistory表中删除了数据，并尝试将新表和列更改迁移到db。这时EF6给我一个错误



数据库中已经有一个名为'xxxx'的对象。。

我尝试过使用此命令的方式，对表列更改没有影响。

I have accidentally deleted data from __MigrationHistory table and I tried to make migration new tables and column changes to db. At this time EF6 show me an error

"There is already an object named 'xxxx' in the database.".
I tried the way by using this command and there is no effect on table column changes.

Add-Migration MyMigration1 -IgnoreChanges
Update-database -Force

有很多关于重建db或其他的建议。但这些方式可能会影响数据丢失到我的数据库，其中包含大量的测试数据，我无法丢失任何数据。如何在不丢失任何数据的情况下解决此错误。如果有人请...



我尝试过：



我尝试使用此命令，并且对表列更改没有影响。

There are many recommendation about this for recreating db or another else. But those ways might be effect data losing to my db which contains a huge size of tested data and I can't able to lost any data. How to solve this error by without losing any data. If anybody please...

What I have tried:

I tried the way by using this command and there is no effect on table column changes.

Add-Migration MyMigration1 -IgnoreChanges
Update-database -Force

推荐答案

运行 Update-Database -Script -SourceMigration：0 为你的数据库生成一个SQL脚本。



然后你需要通过脚本来查找 CREATE TABLE 和 INSERT _MigrationHistory 表的语句，并针对您的数据库运行这些语句。 注意：如果您只删除了数据，并且 _MigrationHistory 表仍然存在，那么您只需要 INSERT 语句。



如果您的所有数据库都已经是最新的，您还可以尝试Rick Strahl描述的方法：

将实体框架迁移重置为干净的Slate - Rick Strahl的Web日志 [ ^ ]

但要注意警告：

Run Update-Database -Script -SourceMigration:0 to generate a SQL script for your database.

You'll then need to pick through the script to find the CREATE TABLE and INSERT statements for the _MigrationHistory table, and run just those statements against your database. NB: If you've only deleted the data, and the _MigrationHistory table still exists, you'll only need the INSERT statements.

If all of your databases are already up-to-date, you could also try the approach described by Rick Strahl:
Resetting Entity Framework Migrations to a clean Slate - Rick Strahl's Web Log[^]
But pay attention to the warning:

Quote：

一旦应用了更新，您的迁移起始点就完全没有数据库，或者处于完全更新的基本状态的数据库。如果在开始清理平板操作之前，您的数据库在迁移中有几次迭代，那么就没有简单的方法可以使这些数据库同步。

Once the updates are applied your migration starting points are either no database at all, or the database in the fully updated base state. If you have databases that were a few iterations behind in migrations before you started the clean slate operations, there will be no easy way to get those in sync.

一旦解决了问题，请备份数据库并设置预定作业以使其备份。下次遇到这样的问题时，您只需从上一次良好的备份恢复即可。

Once you've fixed the problem, back up your database and set up a scheduled job to keep it backed up. Next time you have a problem like this, you will simply be able to restore from the last good backup.

这篇关于从EF6中的__migrationhistory表中删除数据后，如何在不丢失任何数据的情况下进行迁移？的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！