如何删除记录以及ASP.NET（C＃）中的所有相关记录

Question

我有这段代码可以从表中删除摄影师，但是，photograph_id是表“ images”中的外键，当我删除摄影师时，我想删除摄影师在“ images”表中的所有图像删除。 我怎么做？

...

else if (e.CommandName == "Slet")
{
    SqlConnection conn = new SqlConnection();
    conn.ConnectionString =
        ConfigurationManager.ConnectionStrings["DatabaseConnectionString1"].ToString();
    SqlCommand cmd = new SqlCommand();
    cmd.Connection = conn;

    cmd.CommandText = "DELETE FROM photographers WHERE photographer_id = @photographer_id";

    cmd.Parameters.Add("@photographer_id", SqlDbType.Int).Value = e.CommandArgument.ToString();

    conn.Open();
    cmd.ExecuteNonQuery();
    conn.Close();

    Repeater1.DataBind();
}

这是我的IMAGES表：

CREATE TABLE [dbo].[images] (
    [image_id] INT  IDENTITY (1, 1) NOT NULL,
    [image] NVARCHAR (50) NOT NULL,
    [FK_photographer] INT NOT NULL,
    PRIMARY KEY CLUSTERED ([billede_id] ASC),
    CONSTRAINT [FK_fotograf] FOREIGN KEY ([FK_fotograf]) REFERENCES [dbo].[Fotografer] ([fotograf_id]),

);

这是我的PHOTOGRAPHERS表：

CREATE TABLE [dbo].[photographers] (
    [photographer_id] INT IDENTITY (1, 1) NOT NULL,
    [photographer_name] NVARCHAR (50) NOT NULL,
    PRIMARY KEY CLUSTERED ([photographer_id] ASC)
);

Answer 1

在外键约束上设置级联删除 。 s when you delete a摄影师s when you delete a这将自动删除Image。

无需自己动手改造轮子。

Answer 2

相同的方法-

DELETE FROM images WHERE photographer_id = @photographer_id

建议先删除图像，然后再删除摄影师。 如果您的表具有物理FK，则将不允许您在删除所有依赖项之前删除摄影师。

希望这可以帮助。

Answer 3

正如我在评论中提到的，您可以使用级联删除 。 您可以像下面一样更改表格。

ALTER TABLE billeder
ADD CONSTRAINT fk_photographer
FOREIGN KEY (photographer_id)
REFERENCES photographers (photographer_id)
ON DELETE CASCADE;

Answer 4

更好的方法是您可以在“过程”中进行操作，但这是替代和简单的方法

SqlCommand cmd = new SqlCommand();
                        cmd.Connection = conn;
    conn.Open();
    cmd.CommandText = "DELETE FROM photographers WHERE photographer_id = @photographer_id";


cmd.Parameters.Add("@photographer_id", SqlDbType.Int).Value = e.CommandArgument.ToString();


cmd.ExecuteNonQuery();
    //deleted from photographers 

cmd.CommandText = "DELETE FROM Images WHERE photographer_id = @photographer_id";


cmd.Parameters.Add("@photographer_id", SqlDbType.Int).Value = e.CommandArgument.ToString();
     cmd.ExecuteNonQuery();
    //deleted from images