Simple query problem

Hi, How can i change the following query so that i only get unique Booking_ID's: SELECT B.Booking_ID FROM WMS_Bookings B, WMS_Data D WHERE B.Booking_ID = D.Booking_ID AND B.Project_ID = '17' Here are the tables relating to this query: # ---------- MySQL dump ---------- # # Table structure for table 'WMS_Bookings' # CREATE TABLE WMS_Bookings ( Booking_ID int(11) DEFAULT '' NOT NULL auto_increment, User_ID int(11) DEFAULT '0' NOT NULL , Project_ID int(11) DEFAULT '0' NOT NULL , Rep_ID int(11) DEFAULT '0' NOT NULL , PCT_ID int(11) DEFAULT '0' NOT NULL , Practice_ID int(11) DEFAULT '0' NOT NULL , Booking_Start_Date date DEFAULT '0000-00-00' NOT NULL , Booking_End_Date date DEFAULT '0000-00-00' NOT NULL , Booking_Days int(11) DEFAULT '1' NOT NULL , Booking_Hours decimal(3,2) DEFAULT '0.00' NOT NULL , Booking_Mileage int(5) , Booking_Status int(2) DEFAULT '0' NOT NULL , Work_Type varchar(20) DEFAULT '' NOT NULL , Additional_Notes text , PRIMARY KEY (Booking_ID,User_ID,Project_ID,Rep_ID,PCT_ID) ); # # Table structure for table 'WMS_Data' # CREATE TABLE WMS_Data ( Data_ID int(11) DEFAULT '' NOT NULL auto_increment, Data int(11) DEFAULT '0' NOT NULL , Field_ID int(11) DEFAULT '0' NOT NULL , Booking_ID int(11) DEFAULT '0' NOT NULL , PRIMARY KEY (Data_ID) ); # ----------- Dump ends ----------- When i run the query i get the following result: Booking_ID 45 45 47 47 Thanks for your help :)