Question

Connection.Open();
    SqlCommand Command = new SqlCommand(null, Connection);
    Command.CommandText = "Insert into [EmployeeTable] (Forename,Surname,DateofBirth,Email address,Country,Address,City,Postcode,Skill1,Skill2,Skill3,Job1,Job 2,Job3,EmployeeAvailability) Values(@forename, @surname, @dateofbirth, @emailaddress, @phonenumber, @country, @address, @city, @postcode, @skill1, @skill2, @skill3, @job1, @job2, @job3, @employeeavailability)";
    Command.Parameters.AddWithValue("@forename", ForenameInputBox.Text);
    Command.Parameters.AddWithValue("@surname", SurnameInputBox.Text);
    Command.Parameters.AddWithValue("@dateofbirth", DoBInputBox.Text);
    Command.Parameters.AddWithValue("@emailaddress", EmailInputBox.Text);
    Command.Parameters.AddWithValue("@country", CountryInputBox.Text);
    Command.Parameters.AddWithValue("@address", AddressInputBox.Text);
    Command.Parameters.AddWithValue("@city", CityInputBox.Text);
    Command.Parameters.AddWithValue("@postcode", PostcodeInputBox.Text);
    Command.Parameters.AddWithValue("@skill1", Skill1InputBox.Text);
    Command.Parameters.AddWithValue("@skill2", Skill2InputBox.Text);
    Command.Parameters.AddWithValue("@skill3", Skill3InputBox.Text);
    Command.Parameters.AddWithValue("@job1", Job1InputBox.Text);
    Command.Parameters.AddWithValue("@job2", Job2InputBox.Text);
    Command.Parameters.AddWithValue("@job3", Job3InputBox.Text);
    Command.Parameters.AddWithValue("@employeeavailability", EmployeeAvailablityBox.Text);
    Command.ExecuteNonQuery();
    Connection.Close();
}

}

CREATE TABLE [dbo].[EmployeeTable] (
[EmployeeID]            INT           NOT NULL,
[Forename]              NVARCHAR (50) NOT NULL,
[Surname]               NVARCHAR (50) NOT NULL,
[DateofBirth]         DATETIME      NOT NULL,
[Emailaddress]         NVARCHAR (50) NOT NULL,
[Country]               NVARCHAR (50) NOT NULL,
[Address]               NVARCHAR (50) NOT NULL,
[City]                  NVARCHAR (50) NOT NULL,
[Postcode]              NVARCHAR (50) NOT NULL,
[Skill1 ]              NVARCHAR (50) NOT NULL,
[Skill2]               NVARCHAR (50) NOT NULL,
[Skill3]               NVARCHAR (50) NOT NULL,
[Job1]                BIT           NOT NULL,
[Job2]                BIT           NOT NULL,
[Job3]                 BIT           NOT NULL,
[EmployeeAvailability] BIT           NOT NULL,
PRIMARY KEY CLUSTERED ([EmployeeID] ASC)

）;

我创建了一个表来存储员工的详细信息，但是在尝试保存输入时会出现错误消息。错误消息如下：

类型＆＃39; System.Data.SqlClient.SqlException＆＃39;未处理的异常发生在System.Data.dll中附加信息：无法将值NULL插入列＆＃39; EmployeeID＆＃39;，table＆＃39; C：\ USERS \ USER \ DOCUMENTS \ VISUAL STUDIO 2015 \ PROJECTS \ WPFAPPLICATION \ WPFAPPLICATION1 \ EMPLOYEEDB.MDF. dbo.EmployeeTable＆＃39 ;;列不允许空值。 INSERT失败。该声明已被终止

我认为这是因为没有任何值输入到EmployeeID字段中，所以如何设置它以便每次生成一个新的员工ID并填充该字段，假设这是错误消息的原因？

Answer 1

标准方法是将列设为IDENTITY列：

[EmployeeID]   INT   IDENTITY(1,1),

然后数据库将自动生成每个插入的数字。这具有保证唯一性的额外好处，这一点很重要，因为此列也用作主键。由于IDENTITY始终是一个增加的值，因此成为CLUSTERED索引也会很好。

如何在C＃Visual Studio中自动填充字段？

1 个答案: