Question

在我的应用程序中，用户将插入一本书。例如，someBook将插入3个副本。 Table1.BookID = 1，Table1.Copy = 3，然后在另一个表中，这3本书将拥有其主键，因此它将是Table2.AccessionID = 1,2,3 Table2.BookID = 1,1,1。

这就是我目前正在做的事情，但正如Aaron Bertrand所说的那样糟糕。

int BookTitlesID;
public void addBookTitle()
{
  int copy = int.Parse(textBox2.Text);
  try
  {
    using (SqlConnection myDatabaseConnection = new SqlConnection(myConnectionString.ConnectionString))
    {
      myDatabaseConnection.Open();

      using (SqlCommand mySqlCommand1 = new SqlCommand("INSERT INTO BookTitles(BookTitle, Copies) Values(@BookTitle,  @Copies)", myDatabaseConnection))
      {
        mySqlCommand1.Parameters.AddWithValue("@BookTitle", BookTitletextBox.Text);
        mySqlCommand1.Parameters.AddWithValue("@Copies", copy);
        mySqlCommand1.ExecuteNonQuery();
      }
    }
  }
  catch (Exception Ex)
  {
    MessageBox.Show(Ex.Message, "Exception");
  }
}

public void addBook()
{
  int copy = int.Parse(textBox2.Text);
  try
  {
    for (int x = 0; x < copy; x++)
    {
      using (SqlConnection myDatabaseConnection = new SqlConnection(myConnectionString.ConnectionString))
      {
        myDatabaseConnection.Open();
        using (SqlCommand mySqlCommand1 = new SqlCommand("INSERT INTO book(BookTitleID) Values(@BookTitleID)", myDatabaseConnection))
        {
          mySqlCommand1.Parameters.AddWithValue("@BookTitleID", BookTitlesID);
          mySqlCommand1.ExecuteNonQuery();
        }
      }
    }
  }
  catch (Exception Ex)
  {
    MessageBox.Show(Ex.Message, "Exception");
  }
}

private void Form_Load(object sender, EventArgs e)
{
  using (SqlConnection myDatabaseConnection = new SqlConnection(myConnectionString.ConnectionString))
  {
    myDatabaseConnection.Open();
    using (SqlCommand mySqlCommand1 = new SqlCommand("SELECT TOP 1 BookTitleID + 1 FROM BookTitles ORDER BY BookTitleID DESC", myDatabaseConnection))
    {
      string x = mySqlCommand1.ExecuteScalar().ToString();
      BookTitlesID = Convert.ToInt32(x);
    }
  }
}

private void button1_Click(object sender, EventArgs e)
{
  addBookTitle();
  addBook();
}

Answer 1

简化。最值得注意的是，as discussed in your other, related question，出去看看当前MAX的内容绝对没有安全性，加1，并假设这将是下一个生成的身份值。如果在插入后检索它，则只能依赖该数字，最可靠的方法是使用SCOPE_IDENTITY()（或者，对于多行{{1 }，INSERT子句。

OUTPUT

现在你可以真正简化你的C＃代码（我不是C＃代码，所以这是否是最好的方法，或者它是否会编译甚至超出我，但希望你可以自己解决这个问题。） / p>
CREATE PROCEDURE dbo.InsertBook @BookTitle NVARCHAR(256), @Copies INT AS BEGIN SET NOCOUNT ON; DECLARE @BookTitleID INT; INSERT dbo.BookTitles(BookTitle, Copies) SELECT @BookTitle, @Copies; SELECT @BookTitleID = SCOPE_IDENTITY(); INSERT dbo.Books(BookTitleID) SELECT @BookTitleID FROM (SELECT TOP (@Copies) rn = ROW_NUMBER() OVER (ORDER BY [object_id]) FROM sys.all_objects ORDER BY [object_id]) AS y; END GO

在表中插入的正确方法然后将其复制到另一个表

1 个答案: