EF核心更新数据库错误“操作数类型冲突：日期与smallint不兼容”

Question

EF Core Update-Database failed when i try change column type from datetime to smallint: "Operand type clash: date is incompatible with smallint"

Migration file:

public partial class BookYearFieldChanged : Migration

{
    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

create a new column with required datatype, update the new column with required data and drop the previous column.

 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