How to run multiple SQL commands in a single SQL connection?

问题

I am creating a project in which I need to run 2-3 sql commands in a single sql connection. Here is the code I have written:

SqlConnection con = new SqlConnection(@\"Data Source=(LocalDB)\\v11.0;AttachDbFilename=|DataDirectory|\\project.mdf;Integrated Security=True\");
con.Open();
SqlCommand cmd = new SqlCommand(\"select *  from \" + mytags.Text + \" \", con);
SqlDataReader rd = cmd.ExecuteReader();
if (rd.Read())
{
    con.Close();
    con.Open();
    SqlCommand cmd1 = new SqlCommand(\"insert into \" + mytags.Text + \" values (\'fname.lname@gmail.com\',\'\" + TextBox3.Text + \"\',\'\" + TextBox4.Text + \"\',\'\" + TextBox5.Text + \"\',\'\"+mytags.Text+\"\')\", con);
    cmd1.ExecuteNonQuery();
    label.Visible = true;
    label.Text = \"Date read and inserted\";
}
else
{
    con.Close();
    con.Open();
    SqlCommand cmd2 = new SqlCommand(\"create table \" + mytags.Text + \" ( session VARCHAR(MAX) , Price int , Description VARCHAR(MAX), Date VARCHAR(20),tag VARCHAR(10))\", con);
    cmd2.ExecuteNonQuery();
    con.Close();
    con.Open();
    SqlCommand cmd3 = new SqlCommand(\"insert into \" + mytags.Text + \" values (\'\" + Session + \"\',\'\" + TextBox3.Text + \"\',\'\" + TextBox4.Text + \"\',\'\" + TextBox5.Text + \"\',\'\" + mytags.Text + \"\')\", con);
    cmd3.ExecuteNonQuery();
    label.Visible = true;
    label.Text = \"tabel created\";
    con.Close();
}

I have tried to remove the error and I got that the connection is not going to else condition. Please review the code and suggest if there is any mistake or any other solution for this.

回答1:

Just change the SqlCommand.CommandText instead of creating a new SqlCommand every time. There is no need to close and reopen the connection.

// Create the first command and execute
var command = new SqlCommand("<SQL Command>", myConnection);
var reader = command.ExecuteReader();

// Change the SQL Command and execute
command.CommandText = "<New SQL Command>";
command.ExecuteNonQuery();

回答2:

The following should work. Keep single connection open all time, and just create new commands and execute them.

using (SqlConnection connection = new SqlConnection(connectionString))
{
    connection.Open();
    using (SqlCommand command1 = new SqlCommand(commandText1, connection))
    {
    }
    using (SqlCommand command2 = new SqlCommand(commandText2, connection))
    {
    }
    // etc
}

回答3:

Just enable this property in your connection string:

sqb.MultipleActiveResultSets = true;

This property allows one open connection for multiple datareaders.

回答4:

I have not tested , but what the main idea is: put semicolon on each query.

SqlConnection connection = new SqlConnection();
SqlCommand command = new SqlCommand();
connection.ConnectionString = connectionString; // put your connection string
command.CommandText = @"
     update table
     set somecol = somevalue;
     insert into someTable values(1,'test');";
command.CommandType = CommandType.Text;
command.Connection = connection;

try
{
    connection.Open();
}
finally
{
    command.Dispose();
    connection.Dispose();
}

Update: you can follow Is it possible to have multiple SQL instructions in a ADO.NET Command.CommandText property? too

回答5:

This is likely to be attacked via SQL injection by the way. It'd be worth while reading up on that and adjusting your queries accordingly.

Maybe look at even creating a stored proc for this and using something like sp_executesql which can provide some protection against this when dynamic sql is a requirement (ie. unknown table names etc). For more info, check out this link.

回答6:

Here you can find Postgre example, this code run multiple sql commands (update 2 columns) within single SQL connection

public static class SQLTest
    {
        public static void NpgsqlCommand()
        {
            using (NpgsqlConnection connection = new NpgsqlConnection("Server = ; Port = ; User Id = ; " + "Password = ; Database = ;"))
            {
                NpgsqlCommand command1 = new NpgsqlCommand("update xy set xw = 'a' WHERE aa='bb'", connection);
                NpgsqlCommand command2 = new NpgsqlCommand("update xy set xw = 'b' where bb = 'cc'", connection);
                command1.Connection.Open();
                command1.ExecuteNonQuery();
                command2.ExecuteNonQuery();
                command2.Connection.Close();
            }
        }
    }

回答7:

Multiple Non-query example if anyone is interested.

using (OdbcConnection DbConnection = new OdbcConnection("ConnectionString"))
{
  DbConnection.Open();
  using (OdbcCommand DbCommand = DbConnection.CreateCommand())
  {
    DbCommand.CommandText = "INSERT...";
    DbCommand.Parameters.Add("@Name", OdbcType.Text, 20).Value = "name";
    DbCommand.ExecuteNonQuery();

    DbCommand.Parameters.Clear();
    DbCommand.Parameters.Add("@Name", OdbcType.Text, 20).Value = "name2";
    DbCommand.ExecuteNonQuery();
  }
}

来源：https://stackoverflow.com/questions/13677318/how-to-run-multiple-sql-commands-in-a-single-sql-connection

标签

sql-server

ado.net

sqlconnection

sqlcommand