如果尚未创建，如何从C＃以编程方式创建MySQL触发器？

Question

I would like to create the trigger programmatically only if not created.

I am not able to create trigger programmatically from C# . If I am executing the same trigger from MySQL Workbench 6.3 than its successfully created the trigger.

I am receiving the error while executing from C# as below.

Error at line

cmd.ExecuteNonQuery(). "You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'DELIMITER // CREATE TRIGGER Trigger_Lifetouch AFTER INSERT ON mat.lifetou' at line 1"

My Code as below

public void createTrigger()
    {
            string _query = " DELIMITER // " +
                            " CREATE "+
                            " TRIGGER `Trigger_Lifetouch`  AFTER INSERT  "+
                            " ON mat.lifetouch "+
                            " FOR EACH ROW BEGIN "+
                            " INSERT INTO mat.lifetouchrespirationrate (ByDevSessionId) VALUES(2);       "+
                            " END;" ;

            using (MySql.Data.MySqlClient.MySqlConnection con = new MySql.Data.MySqlClient.MySqlConnection(connectionstring))
            {
                using (var cmd = con.CreateCommand())
                {
                    if (con.State == ConnectionState.Closed || con.State == ConnectionState.Broken)
                    {
                        con.Open();
                    }

                    int retn = 0;

                    using (var transaction = con.BeginTransaction(IsolationLevel.ReadCommitted))
                    {
                        retn = 0;
                        cmd.Transaction = transaction;
                        cmd.CommandText = _query;

                        try
                        {
                            retn = Convert.ToInt32(cmd.ExecuteNonQuery().ToString());

                            if (retn > 0)
                            {
                                logger.Debug(" Trigger Created ");
                            }
                            else
                            {
                                logger.Debug("  Trigger Not Created  ");
                            }
                        }
                        catch (Exception ex)
                        {
                            logger.Debug(ex );
                        }

                    }
                }
            }

Answer 1

Try to copy at runtime value from variable _query and paste it to MySql Query editor. It's an error when you construct the query. You forgot to add at the end "DELIMITER ;"

Answer 2

Trigger creation can not not be done through MySqlCommand. you should use (new MySqlScript([ConnectionString], [TriggerScript])).Execute();

this will create the trigger.

Answer 3

try and used @ in creating a queries

string _query = @" DELIMITER //
                   CREATE
                   TRIGGER `Trigger_Lifetouch`  AFTER INSERT
                   ON mat.lifetouch
                   FOR EACH ROW BEGIN
                   INSERT INTO mat.lifetouchrespirationrate (ByDevSessionId) VALUES(2);       
                   END
                   //;" ;