Question

I’m supporting an application in which we need to migrate the code first generated database. The change is to modify three properties (all on the same table/entity) from a string to a nullable decimal.

Part of the requirement of doing this is that I need to output the changes to a SQL file, since we a deploying the patch to our client, who is also hosting the product in production.

I was told that this is possible but I am unsure how to do it.

Question: How can I, using EF code first, migrate the database table to have nullable decimals instead of strings and have the changes outputted to a SQL file. I am making the assumption that all the values currently in the column are convertible to decimals, but if not how would that change the complexity?

Answer 1

If I’m correct in the requirements, then you’ll need to create a migration, then run

Update-Database -Script

This will create a sql script that will be run against the DB to update the structure.

Also Update-Database -Verbose will update the DB structure, and output the SQL run.

If you need to preserve the data, you can also run SQL in your migration script directly:

public partial class RenameColumn : DbMigration
{
    public override void Up()
    {
       Sql("update blah...");
    }

    public override void Down()
    {
      Sql("drop table bobby");
    }

And there you can do whatever you need to do to preserve the data: add temp colum/table, copy original data there, change the column type, convert the data to a required format and copy it to the new column, clean-up.

If you have Sql command in the migration, when you run Update-Database -Script, it will give you combined script – scaffolded migration script and your manually written script.