How to read data from SQL server and update SharePoint list

It's a simple example via c# SSOM to retrieve Records from SQLdatabase table to existing SharePoint list

1. Create a function to get your data from SQL server and return it to a data table.

    // your method to pull data from database to datatable   
    public DataTable GetDatafromSQL()
    {
        DataTable dataTable = new DataTable();            
        string connString = @"your connection string here";
        string query = "select * from table";

        SqlConnection conn = new SqlConnection(connString);        
        SqlCommand cmd = new SqlCommand(query, conn);
        conn.Open();

        // create data adapter
        SqlDataAdapter da = new SqlDataAdapter(cmd);
        // this will query your database and return the result to your datatable
        da.Fill(dataTable);
        conn.Close();
        da.Dispose();
        return dataTable;
    }

2. Create a function that loop for every item at the retrieved SQL data table and adds it to list.

     void binditems()
     {
         DataTable dt = new DataTable();
         dt= GetDatafromSQL();

     using (SPSite oSite=new SPSite("http://mysharepoint"))
      {

       using (SPWeb oWeb=oSite.RootWeb)
        {
            SPList oList = oWeb.Lists["Test"];
            foreach (DataRow row in dt.Rows) // Loop over the rows.
            {
            SPListItem oSPListItem = oList.Items.Add();
            oSPListItem["Title"] = row["Title"].ToString();
            oSPListItem.Update();
            }
        }
     }
     }

Read the Function binditems(), to can bind the data from SQL to List

Note : don't forget to include this namespaces using System.Data.SqlClient; using Microsoft.SharePoint;