Need to insert a data row multiple times in the database - asp.net

Question

I have two data tables in sql. I need to insert data feom one table to another. My first data table Table1 contain data column Code,Model,Num,Qty and second table Table2 also contain the same. But I need to insert the data from table1 to table2 multiple times. If Qty in Table1 is 4 then, insert the data of
Table1 for 4 times according to the quantity.
protected void Button15_Click3(object sender, EventArgs e)
{
for (int i = 0; i < 4; i++)
{
String str1 = "insert into Table2(Code, Model, Num, Qty) select Code, Model, Num, Qty from Table1;";
SqlCommand xp1 = new SqlCommand(str1, con);
con.Open();
SqlDataAdapter da1 = new SqlDataAdapter();
da1.SelectCommand = xp1;
DataSet ds1 = new DataSet();
da1.Fill(ds1, "Code");
GridView1.DataSource = ds1;
con.Close();
}
}
}
In this program I give Number 4 manually, but I need to take it from my database qty. How can I put the SQL column name qty in the loop to insert the data at multiple time?

Answer 1

You can give a try like this:
private void button1_Click(object sender, EventArgs e)
{
string connetionString = null;
SqlConnection connection ;
SqlDataAdapter adapter = new SqlDataAdapter();
DataSet ds = new DataSet();
int i = 0;
int j = 0;
connetionString = "Data Source=ServerName;Initial Catalog=DatabaseName;User ID=UserName;Password=Password";
connection = new SqlConnection(connetionString);
try
{
connection.Open();
adapter.SelectCommand = new SqlCommand("Your SQL Statement Here", connection);
adapter.Fill(ds);
connection.Close();
for(j=0;j<=ds.Tables[0].Rows.Count;j++){
for (i = 0; i <= Convert.ToInt32(ds.Tables[0].Rows[j]["Qty"].ToString()); i++)
{
String str1 = "insert into Table2(Code, Model, Num, Qty)
select Code, Model, Num, Qty from Table1;";
SqlCommand xp1 = new SqlCommand(str1, con);
con.Open();
SqlDataAdapter da1 = new SqlDataAdapter();
da1.SelectCommand = xp1;
DataSet ds1 = new DataSet();
da1.Fill(ds1, "Code");
GridView1.DataSource = ds1;
con.Close();
}
}
}
catch (Exception ex)
{
MessageBox.Show(ex.ToString());
}
}
I hope it is clear now. !

Answer 2

As pointed out in the comments, duplicating rows isn't a good idea without a primary key on both the source and destination tables, as otherwise identification of rows will become problematic.
You haven't mentioned whether you want to copy just one row, multiple rows, or the whole table N times over, but assuming the latter, bulk IO jobs like this is better suited to doing the whole operation within the database server, in order to reduce the IO transferring data back and forth between your app and the database.
Assuming both tables are in the same database, here's a way you can do this with a row-duplicating recursive CTE. If you need to control the #CopyCount from C#, just bind it as an integer and execute it with SqlCommand.ExecuteNonQuery:
DECLARE #CopyCount INT = 10;
with cteRowGen AS
(
SELECT 1 AS RowNum
UNION ALL
SELECT RowNum + 1
FROM cteRowGen
WHERE RowNum < #CopyCount
)
insert into Table2(Code,Model,Num,Qty)
select Code,Model,Num,Qty
from table1 CROSS JOIN cteRowGen;

Answer 3

Like StuartLC pointed out, CTE is the way to go.
Here's a version that will read the QTY from your table1
It will also insert 1 for the Qty in Table2, and not 4
DECLARE #Cnt INT = (SELECT Qty FROM Table1);
WITH data AS (
SELECT 1 AS RowCnt
UNION ALL
SELECT RowCnt + 1
FROM data
WHERE RowCnt < #Cnt
)
INSERT INTO Table2
SELECT Code, Model, Num, 1 as Qty
FROM Table1 a
CROSS JOIN data