count the total number of launch site of the rockets which have been launched form cape canaveral air force station launch complex 18 ?
SELECT DISTINCT COUNT attr_open var_uri attr_close where brack_open var_x dbo_launchSite dbr_Cape_Canaveral_Air_Force_Station_Launch_Complex_18 sep_dot var_x dbo_launchSite var_uri brack_close