Question

I’m creating a temporary table, #ua_temp, which is a subset of regular table. I don’t get an error, but when I try to SELECT from #ua_temp in the second step, it’s not found. If I remove the #, a table named ua_temp is created.

I’ve used the exact same technique from created the table with SELECT INTO elsewhere. It runs fine, so I don’t think it has anything to do with database settings. Can anyone see the problem?

        // Create temporary table 
        q = new StringBuilder(200);
        q.Append("select policy_no, name, amt_due, due_date, hic, grp, eff_dt, lis_prem, lis_grp, lis_co_pay_lvl, ");
        q.Append("lep_prem, lapsed, dn_code, [filename], created_dt, created_by ");
        q.Append("into #ua_temp from elig_ua_response ");
        q.Append("where [filename] = @fn1 or [filename] = @fn2 ");
        sc = new SqlCommand(q.ToString(), db);
        sc.Parameters.Add(new SqlParameter("@fn1", sFn));
        sc.Parameters.Add(new SqlParameter("@fn2", sFn2));
        int r = sc.ExecuteNonQuery();
        MessageBox.Show(r.ToString() + " rows");

        // Rosters
        q = new StringBuilder(200);
        q.Append("select policy_no,name,amt_due,due_date,hic,grp,eff_dt,");
        q.Append("lis_prem,lis_grp,lis_co_pay_lvl,lep_prem,lapsed,dn_code,[filename] ");
        q.Append("from #ua_temp where (lis_prem > 0.00 or lep_prem > 0.00) ");
        q.Append("and [filename] = @fn order by name");
        sc.CommandText = q.ToString();
        sc.Parameters.Clear();
        sc.Parameters.Add(new SqlParameter("@fn", sFn));
        sda = new SqlDataAdapter(sc);
        sda.Fill(ds, "LIS LEP Roster");

To answer some of the obvious questions: This program was running fine using the source table, elig_ua_response. The reason for introducing the temp table was that I want to delete some of the rows for this particular report. I put brackets around the column [filename] while testing to be sure it’s not a key word issue. The second SELECT works fine if you replace #ua_temp with elig_ua_response. I’ve tried different names for the temp table. The MessageBox showing the number of rows was just for debugging purposes; it doesn’t affect the problem.

Answer 1

I think the solution to your problem is to combine the creation of the temp table and selecting from that temp table into one query (see code snippet #3 below). Executing the command twice (as you do in the code in your question) seems to work ok if you are not using command parameters, but fails if they are introduced. I tested a few different approaches and here’s what I found.

1) WORKS OK: Use same command object, no command parameters, execute command twice:

using (var conn = new SqlConnection("..."))
{
    conn.Open();
    using (var cmd = conn.CreateCommand())
    {
        const string query = @"
            CREATE TABLE #temp 
                ([ID] INT NOT NULL, [Name] VARCHAR(20) NOT NULL)
            INSERT INTO #temp VALUES(1, 'User 1')
            INSERT INTO #temp VALUES(2, 'User 2')";
        cmd.CommandType = CommandType.Text;
        cmd.CommandText = query;
        cmd.ExecuteNonQuery();

        cmd.CommandText = "SELECT * FROM #temp";
        using (var sda = new SqlDataAdapter(cmd))
        {
            var ds = new DataSet();
            sda.Fill(ds);
            foreach (DataRow row in ds.Tables[0].Rows)
                Console.WriteLine("{0} - {1}", row["ID"], row["Name"]);
        }
    }
}

2) FAILS: Use same command object, command parameters, execute command twice:

using (var conn = new SqlConnection("..."))
{
    conn.Open();
    using (var cmd = conn.CreateCommand())
    {
        const string query = @"
            CREATE TABLE #temp 
                ([ID] INT NOT NULL, [Name] VARCHAR(20) NOT NULL)
            INSERT INTO #temp VALUES(1, @username1)
            INSERT INTO #temp VALUES(2, @username2)
        ";
        cmd.CommandType = CommandType.Text;
        cmd.CommandText = query;
        cmd.Parameters.Add("@username1", SqlDbType.VarChar).Value ="First User";
        cmd.Parameters.Add("@username2", SqlDbType.VarChar).Value ="Second User";
        cmd.ExecuteNonQuery();

        cmd.Parameters.Clear();
        cmd.CommandText = "SELECT * FROM #temp";
        using(var sda = new SqlDataAdapter(cmd))
        {
            var ds = new DataSet();
            sda.Fill(ds);
            foreach(DataRow row in ds.Tables[0].Rows)
                Console.WriteLine("{0} - {1}", row["ID"], row["Name"]);
        }
    }
}

3) WORKS OK: Use same command object, command parameters, execute command once only:

using (var conn = new SqlConnection("..."))
{
    conn.Open();
    using (var cmd = conn.CreateCommand())
    {
        const string query = @"
            CREATE TABLE #temp 
                ([ID] INT NOT NULL, [Name] VARCHAR(20) NOT NULL)
            INSERT INTO #temp VALUES(1, @username1)
            INSERT INTO #temp VALUES(2, @username2)
            SELECT * FROM #temp
        ";
        cmd.CommandType = CommandType.Text;
        cmd.CommandText = query;
        cmd.Parameters.Add("@username1", SqlDbType.VarChar).Value ="First User";
        cmd.Parameters.Add("@username2", SqlDbType.VarChar).Value ="Second User";
        using (var sda = new SqlDataAdapter(cmd))
        {
            var ds = new DataSet();
            sda.Fill(ds);
            foreach (DataRow row in ds.Tables[0].Rows)
                Console.WriteLine("{0} - {1}", row["ID"], row["Name"]);
        }
    }
}