如何在SQL Server中插入100000行？

INSERT INTO mytable (column1, column2, column3)
SELECT column1, column2, column3
FROM mytable_0
UNION ALL
SELECT column1, column2, column3
FROM mytable_1
UNION ALL
SELECT column1, column2, column3
FROM mytable_2
UNION ALL
...
SELECT column1, column2, column3
FROM mytable_999
UNION ALL
SELECT column1, column2, column3
FROM mytable_1000

INSERT INTO mytable (column1, column2, column3)
SELECT TOP 1000 column1, column2, column3
FROM mytable_source

INSERT INTO mytable (column1, column2, column3)
SELECT column1, column2, column3
FROM mytable_source
WHERE date_column BETWEEN DATEADD(day, -1000, GETDATE()) AND GETDATE()

List<MyTable> list = new List<MyTable>();
for (int i = 0; i < 1000; i++)
{
    MyTable table = new MyTable();
    table.Column1 = "value1";
    table.Column2 = "value2";
    table.Column3 = "value3";
    list.Add(table);
}
using (SqlConnection connection = new SqlConnection(connectionString))
{
    connection.Open();
    foreach (MyTable item in list)
    {
        SqlCommand command = new SqlCommand("INSERT INTO mytable (column1, column2, column3) VALUES (@column1, @column2, @column3)", connection);
        command.Parameters.AddWithValue("@column1", item.Column1);
        command.Parameters.AddWithValue("@column2", item.Column2);
        command.Parameters.AddWithValue("@column3", item.Column3);
        command.ExecuteNonQuery();
    }
}