mysql - Multiple Where clause with decryption -

would query decrypt usernames each condition or once , apply each condition?

select *  tablea  (     concat_ws(         ' ',          aes_decrypt(tablea.firstname, "fnkey"),          aes_decrypt(tablea.lastname, "lnkey")     ) '%ray%'      or      concat_ws(         ' ',          aes_decrypt(tablea.lastname, "lnkey"),          aes_decrypt(tablea.firstname, "fnkey")     ) '%ray%' ); 

i cannot tell if function evaluated once each row or more. depends on query optimizer. establish benchmark.

anyway, query inefficient. full table scan , calculate function each row. cannot use index here. not implement query on table more couple of rows.