mysql - Query Optimization (Function Vs SubQuery) -

in mysql better use function(included subquery) in store procedure instead of direct writing subquery, make difference or code reuse?

the answer quite simple: give try , measure results; preferably on test-set realistic. (you might not see difference when there 2 records in table, effect on 2 million records gigantic)

you can test in way:

$starttime = microtime(true); // codes $endtime = microtime(true); echo $duration = $endtime - $starttime; 

imho, subquery (a lot) faster same functionality stored in function. i'm mssql-biased , can't quite tell if mysql different; doubt it.