SQL - INSERT with Scope_Identity() - getting the r

问题:

I have an ASP.NET page written in VB.NET that gets the items into a GridView by using a SELECT statement with INNER JOIN and also allows you to add an item to the invoice.

INNER JOIN that gets data from items and project_items.

SELECT Items.item_id, Items.item_name, Items.item_cost, project_items.item_quantity
FROM Items 
INNER JOIN project_items
ON items.item_id = project_items.item_id 
WHERE project_items.project_id = @parameter

@parameter is Session("ProjectID")

(There is a foreign key project_items.item_id -> items.item_id.)

I have an trying to use an SQL statement in VB.NET to try and INSERT into two tables simultaneously. What I tried is I tried to get the item_id of the last record created and insert into another table (project_items) by using that data. However, data is only being entered into the first table.

Any idea what I can do?

This is the code:

Protected Sub btnAddItem_Click(sender As Object, e As EventArgs) Handles btnAddItem.Click

        Dim conn As New SqlConnection("Data Source=BRIAN-PC\SQLEXPRESS;Initial Catalog=master_db;Integrated Security=True")
        Dim addItemComm As String = "SELECT item_id FROM project_items WHERE project_id=@ProjectID"
        Dim user_id_select As New Integer

        Dim addItemSQL As New SqlCommand

        conn.Open()

        addItemSQL = New SqlCommand(addItemComm, conn)
        addItemSQL.Parameters.AddWithValue("@ProjectID", Convert.ToInt32(Session("ProjectID")))


        Dim datareader As SqlDataReader = addItemSQL.ExecuteReader()


        datareader.Close()
        conn.Close()

        Dim AddNewItemComm As String = "INSERT INTO Items (item_name,  item_cost, item_code) VALUES (@ItemName, @ItemCost, @ItemCode); SELECT SCOPE_IDENTITY()"
        Dim AddNewItem2Comm As String = "INSERT INTO project_items (item_id, project_id, item_quantity) VALUES (@ItemID, @ProjectID, @ItemQuantity) "
        Dim AddNewItemSQL As New SqlCommand


        conn.Open()

        AddNewItemSQL = New SqlCommand(AddNewItemComm, conn)
        AddNewItemSQL.Parameters.AddWithValue("@ItemName", txtItemName.Text.Trim)
        AddNewItemSQL.Parameters.AddWithValue("@ItemCost", Convert.ToInt32(txtItemCost.Text))
        AddNewItemSQL.Parameters.AddWithValue("@ItemCode", txtItemCost.Text.ToString.ToUpper)

        Dim ItemId As Integer

        ItemId = AddNewItemSQL.ExecuteScalar()

        AddNewItemSQL.ExecuteNonQuery()

        conn.Close()

        conn.Open()

        AddNewItemSQL = New SqlCommand(AddNewItem2Comm, conn)

        AddNewItemSQL.Parameters.AddWithValue("@ItemID", ItemId)
        AddNewItemSQL.Parameters.AddWithValue("@ProjectID", Convert.ToInt32(Session("ProjectID")))
        AddNewItemSQL.Parameters.AddWithValue("@ItemQuantity", Convert.ToInt32(txtItemQuantity.Text))

        AddNewItemSQL.ExecuteNonQuery()

        conn.Close()



    End Sub

回答1:

Why are you doing this in multiple statements in the first place? Why not:

INSERT dbo.Items (item_name,  item_cost, item_code) 
  OUTPUT inserted.ItemID, @ProjectID, @ItemQuantity 
  INTO dbo.project_items(item_id, project_id, item_quantity)
VALUES (@ItemName, @ItemCost, @ItemCode);

Now you only have to call one ExecuteNonQuery() and your app doesn't have to care about the actually SCOPE_IDENTITY() value generated. (You can still retrieve SCOPE_IDENTITY() if you want, of course, using ExecuteScalar - but as Nenad rightly points out, pick one instead of calling both.)

Since we now know that there is an explicit foreign key here, we can still reduce your C# code to one call even if we can't use the OUTPUT clause.

DECLARE @i INT;

INSERT dbo.Items (item_name,  item_cost, item_code) 
  SELECT @ItemName, @ItemCost, @ItemCode;

SELECT @i = SCOPE_IDENTITY();

INSERT dbo.project_items(item_id, project_id, item_quantity)
  SELECT @i, @ProjectID, @ItemQuantity 

SELECT @i; -- if necessary

Would be even cleaner to put this into a stored procedure.

回答2:

ItemId = AddNewItemSQL.ExecuteScalar()

        AddNewItemSQL.ExecuteNonQuery()

These two rows next to each other will execute the command twice. You should remove the second one - ExecuteNonQuery. This will have your data inserted twice in the Items - two same rows but with different IDs.

Since you only retrieve ItemID from the first row, that one should be inserted in project_items, but the other one that was last inserted in items will have no matching row.

Also - complete section from beginning of button click method up before Dim AddNewItemComm As String - where you open and close DataReader and do nothing with it seems completely unnecessary.