UPDATE .. WHERE or INSERT .. ON DUPLICATE KEY UPDATE?

[Daniel Chiaramello]

Hello all.

I was wondering the potential gains of using UPDATE ... WHERE ... instead of IODKU requests, so I performed some quick tests, and I am very puzzled by the fact that the IODKU were (a little) faster that UPDATE...WHERE ones.

I am perfectly aware that my tests are not representative at all, but I was expecting the opposite.

So, my question: in general, should we use UPDATE ... WHERE instruction when we know that the entry already exists, or INSERT ... ON DUPLICATE KEY UPDATE one?

Thanks for your attention,
Daniel