Entity Framework 6 Code First +MVC5+MySql/Oracle使用过程中的两个问题

namespace Snapsia.Web.Models
{
    using System;
    using System.Data.Entity;
    using System.ComponentModel.DataAnnotations.Schema;
    using System.Linq;

    [DbConfigurationType(typeof(MySql.Data.Entity.MySqlEFConfiguration))]
    public partial class SnapsiaContext : DbContext
    {
        public SnapsiaContext()
            : base("name=SnapsiaContext")
        {
        }

        public virtual DbSet<InfluencersUser> InfluencersUser { get; set; }
        protected override void OnModelCreating(DbModelBuilder modelBuilder)
        {
        }
    }
}

set global optimizer_switch=‘derived_merge=OFF‘;

[Table("TB_USER", Schema = "USER_SNAPSIA")]//dbo架构在oracle数据库为用户名
    public partial class TB_USER
    {
        [Key]
        [StringLength(50)]
        public string ID { get; set; }

        [StringLength(50)]
        public string USERNAME { get; set; }

        [StringLength(50)]
        public string PWD { get; set; }
    }

public partial class OrclContext : DbContext
    {
        public OrclContext()
            : base("name=OrclContext")
        {
        }
        public virtual DbSet<TB_USER> TB_USER { get; set; }
        public virtual DbSet<TB_SYYS> TB_SYYS { get; set; }
        public virtual DbSet<TB_CCT> TB_CCT { get; set; }

        protected override void OnModelCreating(DbModelBuilder modelBuilder)
        {
            modelBuilder.HasDefaultSchema("USER_SNAPSIA"); //dbo架构在oracle数据库为用户名

            modelBuilder.Entity<TB_USER>()
                .Property(e => e.ID)
                .IsUnicode(false);
        }
    }