SQL INSERT but avoid duplicates

Question

I want to do some quick inserts but avoid duplicates into a Table. For argument\'s sake lets call it MarketPrices, I\'ve been experimenting with two ways of doing it but not

Answer 1

Another option: create a unique index on the fields (SecurityCode, BuyPrice, SellPrice) in question, issue a simple insert, and let the database decide whether the records are duplicates. The insert will fail on an attempt to insert a duplicate.

Using code (whether external language or SQL proc) to guarantee uniqueness is not strict enough and will ultimately lead to the very duplicates you hope to prevent.