EF Core 更新数据库错误“操作数类型冲突：日期与 smallint 不兼容”

Question

当我尝试将列类型从 datetime 更改为 smallint 时，EF Core 更新数据库失败：“操作数类型冲突：日期与 smallint 不兼容”

迁移文件：

公共部分类 BookYearFieldChanged：迁移

{
    protected override void Up(MigrationBuilder migrationBuilder)
    {
        migrationBuilder.AlterColumn<short>(
            name: "Published",
            table: "Books",
            nullable: false,
            oldClrType: typeof(DateTime),
            oldType: "date");
    }

    protected override void Down(MigrationBuilder migrationBuilder)
    {
        migrationBuilder.AlterColumn<DateTime>(
            name: "Published",
            table: "Books",
            type: "date",
            nullable: false,
            oldClrType: typeof(short));
    }
}

Answer 1

创建具有所需数据类型的新列，使用所需数据更新新列并删除前一列。

CREATE TABLE [dbo].[table1](
	[columr1] [nvarchar](100) NULL,
	[DTime] [datetime] NULL
) 

/*	you can't do like this*/
/*	alter table table1
	alter column Dtime smallint */
 
ALTER TABLE table1 
ADD DTM smallint

UPDATE table1 
SET DTM = CAST(DTime as smallint)

ALTER TABLE table1 
DROP column DTime

sp_rename 'table1.DTM','DTime','column'
GO