连接两个SQL Server表

Question

I'm trying to connect the following 2 tables together:

CREATE TABLE [dbo].[Groups] 
(
    [Group_Id]   INT IDENTITY (1, 1) NOT NULL,
    [Group_Name] NVARCHAR (50) NULL,
    [Group_Desc] NVARCHAR (50) NULL,

    PRIMARY KEY CLUSTERED ([Group_Id] ASC)
);

CREATE TABLE [dbo].[Events] 
(
    [Event_Id] INT IDENTITY (1, 1) NOT NULL,
    [Event_Group_Id] INT null,
    [Event_Type]  NVARCHAR (50) NULL,
    [Event_Title] NVARCHAR (50) NULL,

    PRIMARY KEY CLUSTERED ([Event_Id] ASC),

    CONSTRAINT fk_event_group  
        FOREIGN KEY (Event_Group_Id) REFERENCES Groups (Group_Id)
);

First question: have I created the tables correctly?

I've been able to add to the Events with the following code but I haven't been able to successfully connect the PK of Groups as an FK in Events .

Does anyone have any suggestions?

  SqlConnection conn = new SqlConnection(ConfigurationManager.ConnectionStrings["BallinoraDBConnectionString1"].ConnectionString);
        conn.Open();
        string findGroupOfEvent = "SELECT Group_Id FROM Groups WHERE Group_Name ='" + DropDownListEventGroup.SelectedItem.ToString() + "'";
        int groupId = Convert.ToInt32(findGroupOfEvent);
        string insertQuery = "INSERT INTO Events (Event_Group_Id, Event_Type, Event_Title) VALUES (@GroupEventID, @Type, @Title)";
        SqlCommand com = new SqlCommand(insertQuery, conn);
        com.Parameters.AddWithValue("@GroupEventID", groupId);
        com.Parameters.AddWithValue("@Type", DropDownListEventType.SelectedItem.ToString());
        com.Parameters.AddWithValue("@Title", TextBoxET.Text);
        com.ExecuteNonQuery();
        Response.Redirect("ViewEvents.aspx");
        Response.Write("Registration is successful");
        conn.Close();

UI

Adding Dropdown Items

Answer 1

Change the value in your designer screen shot https://i.stack.imgur.com/c0Ryz.png to 1 and then 2 etc that corresponds to the ids you used in your database table. That is why your code is failing as you cannot convert a string name to an integer. The value is the unique id (int), the name is the display text.

A much better and more maintainable option would be to dynamically generate the list items from the database values when the form/control loads. There are many already asked questions with good answers on this like Databind ASP.NET List of ListItem to DropDownList issue

Answer 2

并在构建下拉列表时从数据库向GroupID描述文本，您可以直接在下面的SQL中使用ID查询组ID而不是组名：

string findGroupOfEvent = "SELECT Group_Id FROM Groups WHERE Group_ID ='" + DropDownListEventGroup.SelectedItem.ToString() + "'"

Answer 3

Can you provide below details, SQL seems to fine and database also looking good:

1. Are you getting value of DropDownListEventGroup from UI and querying global detail table, giving you data.

2. Do you have data in groups table?

Cheers Sudeep