Building commands

Before invoking a query you have to build the structure containing the command and you can do this with gda_command_new ().

The command type we most commonly use is GDA_COMMAND_TYPE_SQL because we will only focus on SQL queries[1]

          typedef enum {
                  GDA_COMMAND_OPTION_IGNORE_ERRORS  = 1,
                  GDA_COMMAND_OPTION_STOP_ON_ERRORS = 1 << 1,
                  GDA_COMMAND_OPTION_BAD_OPTION     = 1 << 2
          } GdaCommandOptions;
          

Here you see an example of creating a command:

          gint
          execute_sql_non_query (GdaConnection *connection, const gchar * buffer)
          {
            GdaCommand *command;
            gint number;
          
            command = gda_command_new (buffer, GDA_COMMAND_TYPE_SQL, GDA_COMMAND_OPTION_STOP_ON_ERRORS);
            number  = gda_connection_execute_non_query (connection, command, NULL);
          
            gda_command_free (command);
          
            return (number);
          }
          

Making non queries

Non queries are queries that does not return data, only the number of rows affected, as a DELETE or an UPDATE. We use gda_connection_execute_non_query()

        gint
        execute_sql_non_query (GdaConnection *connection, const gchar * buffer)
        {
          GdaCommand *command;
          gint number;
        
          command = gda_command_new (buffer, GDA_COMMAND_TYPE_SQL, GDA_COMMAND_OPTION_STOP_ON_ERRORS);
          number  = gda_connection_execute_non_query (connection, command, NULL);
        
          gda_command_free (command);
        
          return (number);
        }
        

Making normal queries

Normal queries are queries that return data (data models). You have two ways to do this:

• gda_data_model_execute_single_command()
• gda_data_model_execute_command()

You can use the first way when you want to invoke only a single command. Second way is used to execute several comma-separated sentences. It is recommended to use gda_connection_execute_single_command (). Here you see an example:

          gboolean
          execute_sql_command (GdaConnection *connection, const gchar * buffer)
          {
            GdaCommand *command;
            GList *list;
            GList *node;
            gboolean errors=FALSE;
          
            GdaDataModel *dm;
          
          
            command = gda_command_new (buffer, GDA_COMMAND_TYPE_SQL, GDA_COMMAND_OPTION_STOP_ON_ERRORS);
            list = gda_connection_execute_command (connection, command, NULL);
            if (list!=NULL)
              for (node=g_list_first(list); node != NULL; node=g_list_next(node))
                {
                  dm=(GdaDataModel *) node->data;
                  if (dm == NULL)
                    {
                      errors=TRUE;
                    }
                  else
                    {
                      show_table (dm);
                      g_object_unref(dm);
                    }
                }
            else
              {
                errors=TRUE;
              }
            gda_command_free (command);
          
            return (errors);
          }