The following method may be used to avoid Cartesian products when you create a join.
	 
 
	  
		-  Usually you should have at least 
		  t-1 join conditions for a join between 
		  t tables.
		
 
 
		-  If there are multi-column primary keys on a referenced table, there should be as many join conditions between the child table and the referenced table as there are columns in the primary key of the referenced table. 
		
 
 
		-  Turn on the 
		  Prohibit Cartesian Products option.