("" OR null) VS NOT(!"" AND NOT NULL) in where clause

Question

Does anyone know if there is a performace differance between the following we parts of a where SQL string in mysql?

   WHERE ...  AND (field = "" OR field IS NULL);

and

  WHERE ...  AND (NOT (field != "" AND field IS NOT NULL));

Answer 1

There is but it is negligibly small, so small I can't tell which would be faster and which slower. It's more of a matter of which is more readable — in this case I would pick the former.

Answer 2

there is no performance difference as such,. its much more about code-readability here,. and of course the first statement is more readable,.

one more thing i would like to add is when thinking about optimizations,. one should not delve into micro-optimizations because that doesnt really add up to increasing performance because the difference is very negligible and u end up wasting time and resources and making your code less readable, less maintainable and less manageable.,

so whenever thinking about optimizations,. profile your code and start out with things like improving ur app design, db design, utilizing caching and so on,. rather then indulging into discussions about whether echo is faster or print (an example)