Hi,
That depends on the database collation – which is accent insensitive in WordPress, which means that all of these are ignored.
I wouldn’t recommend changing the database collation for this (unless you know what you are doing), WordPress is built around case and accent insensitive tables, it could lead to some unexpected issues. Unfortunately however that is the best possible way to get around it, but again I highly recommend not doing that as it means that the database base structure is altered.
You can however try enabling this option. It will force case sensitivity (which also forces accents) for the search queries. It only works however if you are using the regular engine, but it depends on the database engine too, in some cases even that won’t help.
