Science Buddies: "Ask an Expert"

I want to make a Database that'll predict which drug will be suitable for you on the basis of defined parameters such as: Allergic to certain things etc. On the Back end i want to relate SNPs and Genetics: means How individual respond towards a particular drug according to the genes of an individual. The Question is that from which conditions (parameters) defined by people i can predict which SNP he/she would have (If i have an SNP database) because i don't want to sequence the DNA (SNP profile) of that particular person who wanted find that this drug will react me in which way? i just want to tell that person that you'll respond to this drug in this way by collecting the physical or chemical reactions he or she felt after taking that drug or any conditions he/she normally have.