This is a great way to reduce MySQL code/mistakes/annoyance when doing things, take for example this statement:
INSERT IGNORE INTO sometable(CatName) VALUES("someitem");
Notice the "IGNORE", that is what does the magic.
Normally if the entry "someitem" existed you'd get an error message back such as "Duplicate entry for whatever". What I have normally done in PHP or whatever language is manually coded or made a helper function to return true/false if the same result/name already exists in the database.
Just note that the syntax has changed from a normal INSERT.