如何获得LAST_INSERT_ID（）;

Question

I have looked around and I am still confused on how to get the last inserted ID. I added the statment SELECT LAST_INSERT_ID(); at the end of mysql statement i am executing. I am storing the value in prID = Convert.ToInt32(cmd.ExecuteScalar()); This command is creating two instances in my database. I am pretty sure I need to separate these two statements but unsure how to while still getting the last ID.

          try
            {
                Console.WriteLine("Connecting to MySQL...");
                conn.Open();
                string sql = "INSERT INTO pull_requests (repoID, branchID, fileID, prStatus, prComments) VALUES (@rID, @bID, @fID, @prS, @prC); SELECT LAST_INSERT_ID();";
                MySql.Data.MySqlClient.MySqlCommand cmd = new MySql.Data.MySqlClient.MySqlCommand(sql, conn);
                cmd.Parameters.AddWithValue("@rID", RI);
                cmd.Parameters.AddWithValue("@bID", BI);
                cmd.Parameters.AddWithValue("@fID", FI);
                cmd.Parameters.AddWithValue("@prS", 0);
                cmd.Parameters.AddWithValue("@prC", comment);
                prID = Convert.ToInt32(cmd.ExecuteScalar());

                cmd.ExecuteNonQuery();
            }
            catch (Exception ex)
            {
                Console.WriteLine(ex.ToString());
            }
            conn.Close();

Answer 1

You need to only call cmd.ExecuteNonQuery() to execute the insert statement. On the return, the cmd object will have its .LastInsertedId property populated for you.

Like this:

try
{
    Console.WriteLine("Connecting to MySQL...");
    conn.Open();
    string sql = "INSERT INTO pull_requests (repoID, branchID, fileID, prStatus, prComments) VALUES (@rID, @bID, @fID, @prS, @prC);";
    MySql.Data.MySqlClient.MySqlCommand cmd = new MySql.Data.MySqlClient.MySqlCommand(sql, conn);
    cmd.Parameters.AddWithValue("@rID", RI);
    cmd.Parameters.AddWithValue("@bID", BI);
    cmd.Parameters.AddWithValue("@fID", FI);
    cmd.Parameters.AddWithValue("@prS", 0);
    cmd.Parameters.AddWithValue("@prC", comment);
    cmd.ExecuteNonQuery();

    long lastId = cmd.LastInsertedId;
}
catch (Exception ex)
{
    Console.WriteLine(ex.ToString());
}
conn.Close();

Answer 2

执行查询后，使用MySqlCommand.LastInsertedId属性。

Answer 3

Typically, the SELECT last_insert_id() is executed separately, immediately after the INSERT is executed, on the same connection. The result of last_insert_id() is connection specific, so you do not need to worry about other clients "overwriting" yours.

You can even reuse the same command with just cmd.CommandText = "SELECT last_insert_id()";

...but as others have pointed out, and a quick web search has clarified for me, it looks like the MySQL .Net connector you are using already provides that without a second query.