![](/img/trans.png)
[英]Entity framework core multipleDbContext code-first migration of shared entity
[英]Entity framework core, code first migration with data migration
我正在尝试使用EF Core代码首次迁移来对现有表进行反规范化。
我有现有的表LoginEvent
,其数据如下所示:
╔═════════════════════════════════════════════════╗
║ LoginEvent ║
╠════╦══════════╦═══════════╦════════════╦════════╣
║ Id ║ VenueRef ║ VenueName ║ OccurredAt ║ UserId ║
╠════╬══════════╬═══════════╬════════════╬════════╣
║ 1 ║ ven01 ║ Venue 1 ║ 2018-01-29 ║ 5 ║
╠════╬══════════╬═══════════╬════════════╬════════╣
║ 2 ║ ven02 ║ Venue 2 ║ 2018-01-30 ║ 7 ║
╠════╬══════════╬═══════════╬════════════╬════════╣
║ 3 ║ ven01 ║ Venue 1 ║ 2018-02-01 ║ 9 ║
╚════╩══════════╩═══════════╩════════════╩════════╝
public class LoginEvent
{
[Key]
public int Id { get; set; }
public string VenueRef { get; set; }
public string VenueName { get; set; }
public DateTime OccurredAt { get; set; }
public User User { get; set; }
}
我想将其规范化为两个表: LoginEvent
和Venue
,如下所示:
╔═════════════════════════════════════╗
║ LoginEvent ║
╠════╦══════════╦════════════╦════════╣
║ Id ║ VenueRef ║ OccurredAt ║ UserId ║
╠════╬══════════╬════════════╬════════╣
║ 1 ║ ven01 ║ 2018-01-29 ║ 5 ║
╠════╬══════════╬════════════╬════════╣
║ 2 ║ ven02 ║ 2018-01-30 ║ 7 ║
╠════╬══════════╬════════════╬════════╣
║ 3 ║ ven01 ║ 2018-02-01 ║ 9 ║
╚════╩══════════╩════════════╩════════╝
╔══════════════════════╗
║ Venue ║
╠══════════╦═══════════╣
║ VenueRef ║ VenueName ║
╠══════════╬═══════════╣
║ ven01 ║ Venue 1 ║
╠══════════╬═══════════╣
║ ven02 ║ Venue 2 ║
╚══════════╩═══════════╝
现在,我通过添加一个新的Venue
域对象并让LoginEvent
引用它来完成此操作,如下所示:
public class LoginEvent
{
[Key]
public int Id { get; set; }
public string VenueRef { get; set; }
public DateTime OccurredAt { get; set; }
public Venue Venue { get; set; }
public User User { get; set; }
}
public class Venue
{
[Key]
public string VenueRef { get; set; }
public string VenueName { get; set; }
}
然后我创建了一个迁移,(正确地):
Venue
表 VenueName
列 但是,我需要做的是在步骤1和2之间运行数据迁移,以便在删除列之前和设置约束之前将现有场所放在新表中(否则,我将丢失数据和约束失败,因为我没有相关的场地)。
我想像我的数据迁移一样运行这样的东西:
INSERT INTO Venue SELECT DISTINCT VenueRef, VenueName FROM LoginEvent
我该怎么做?
您可以使用migrationBuilder.Sql(theSqlString)
执行任何SQL。
在你的情况下
migrationBuilder.Sql("INSERT INTO Venue SELECT DISTINCT VenueRef, VenueName FROM LoginEvent");
在创建新表Venue
和删除旧列VenueName
之前,在迁移中运行此VenueName
。
另请参阅自定义迁移操作 。
声明:本站的技术帖子网页,遵循CC BY-SA 4.0协议,如果您需要转载,请注明本站网址或者原文地址。任何问题请咨询:yoyou2525@163.com.