Question

我的数据库中有一个表Teacher：

TABLE Teacher
      (
        ID             CHAR (7) NOT NULL ,
        name           VARCHAR (50) NOT NULL ,
        surname        VARCHAR (50) NOT NULL ,
        email          VARCHAR (50) NOT NULL ,
        phone          CHAR (13) NOT NULL
      )

在数据库中，我有一个INSTEAD OF INSERT触发器，用于创建ID以及来自姓氏和号码的电子邮件。我在SQL Server中插入时一切正常。我能做到

INSERT INTO Teacher(name, surname, phone) 
VALUES('John', 'Doe', '+111111111111')

我在这个数据库上实现了ORM。

public static String SQL_INSERT = 
    "INSERT INTO \"Teacher\" VALUES (@ID, @name, @surname, @email, @phone)";

    public static int Insert(Teacher teacher, Database pDb = null)
    {
        Database db;
        if (pDb == null)
        {
            db = new Database();
            db.Connect();
        }
        else
        {
            db = (Database)pDb;
        }

        SqlCommand command = db.CreateCommand(SQL_INSERT);
        PrepareCommand(command, teacher);
        int ret = db.ExecuteNonQuery(command);

        if (pDb == null)
        {
            db.Close();
        }

        return ret;
    }

    private static void PrepareCommand(SqlCommand command, Teacher teacher)
    {
        command.Parameters.AddWithValue("@ID", teacher.ID);
        command.Parameters.AddWithValue("@name", teacher.Name);
        command.Parameters.AddWithValue("@surname", teacher.Surname);
        command.Parameters.AddWithValue("@email", teacher.Email);
        command.Parameters.AddWithValue("@phone", teacher.Phone);
    }

问题是当我尝试从ORM插入时。我必须这样做，因为它不允许我在没有所有强制属性的情况下插入。

Teacher newTeacher  = new Teacher ();

newTeacher.ID = "";
newTeacher.Name= "John";
newTeacher.Surname= "Doe";
newTeacher.Email = "";
newTeacher.Phone= "+111111111111";

TeacherTable.Insert(newTeacher, db);

有没有办法插入而无需在ID和电子邮件中分配空字符串？ it inserts fine，但代码对我来说很糟糕。谢谢你的帮助。

Answer 1

如果使用默认约束定义表，则在插入时将值设置为默认值，而无需触发器...

CREATE TABLE Teacher
(
    ID             CHAR (7) NOT NULL, --don't know what is the content here... In most cases an ID column with INT IDENTITY is perefered
    name           VARCHAR (50) NOT NULL CONSTRAINT DF_Teacher_name    DEFAULT(''),
    surname        VARCHAR (50) NOT NULL CONSTRAINT DF_Teacher_surname DEFAULT('') ,
    email          VARCHAR (50) NOT NULL CONSTRAINT DF_Teacher_email   DEFAULT('') ,
    phone          CHAR (13) NOT NULL    CONSTRAINT DF_Teacher_phone   DEFAULT('')
);

顺便说一句：我不会强迫电话号码适合13个字符......

Answer 2

ORM正在做它应该做的事情。如果表字段可以为空，并且您的变量是未设置的引用类型，那么它应该插入NULL。顺便说一句，字符串是引用类型。

处理此问题最简单的方法之一是向教师类添加一个构造函数，为所有值设置默认值，这样，每次启动新对象时都不必设置它们。

E.g。

public class Teacher
{
    public Teacher()
      {
           ID = "";
           Name= "";
           Surname= "";
           Email = "";
           Phone= "";
      }
    ....
}

然后您可以执行以下操作：

Teacher newTeacher  = new Teacher ();
newTeacher.Name = "Johnny";
TeacherTable.Insert(newTeacher, db);

只设置您需要的变量，所有其他变量将是构造函数中的默认设置。

Answer 3

您可以将PrepareCommand默认为空白。

private static void PrepareCommand(SqlCommand command, Teacher teacher)
{
     command.Parameters.AddWithValue("@ID", teacher.ID ?? "");
     command.Parameters.AddWithValue("@name", teacher.Name);
     command.Parameters.AddWithValue("@surname", teacher.Surname);
     command.Parameters.AddWithValue("@email", teacher.Email ?? "");
     command.Parameters.AddWithValue("@phone", teacher.Phone);
 }

另外，如果它们为null，则根本无法传递它们，然后在触发器中提供默认值。

private static void PrepareCommand(SqlCommand command, Teacher teacher)
{
    if(string.IsNullOrEmpty(teacher.ID))
        command.Parameters.AddWithValue("@ID", teacher.ID);
    command.Parameters.AddWithValue("@name", teacher.Name);
    command.Parameters.AddWithValue("@surname", teacher.Surname);
    if(string.IsNullOrEmpty(teacher.Email))        
        command.Parameters.AddWithValue("@email", teacher.Email);
    command.Parameters.AddWithValue("@phone", teacher.Phone);
}

这两个都可以让你创建教师对象，如...

Teacher newTeacher  = new Teacher ();

newTeacher.Name= "John";
newTeacher.Surname= "Doe";
newTeacher.Phone= "+111111111111";

TeacherTable.Insert(newTeacher, db);

C＃INSERT INSTEAD OF INSERT TRIGGER

3 个答案: