To use the SDK and QtCreator directly, copy these libraries to your C:\Qt\...\qt\plugins\sqldrivers\, and copy C:\MySQL\MySQL51\lib\opt\libmysql.dll to your C:\Qt\...\qt\bin\.
I has copied these libraries to my C:\QtSDK\QtCreator\bin\sqldrivers and copied C:\xampp\mysql\lib\opt\libmysql.dll to my C:\QtSDK\QtCreator\bin\. but it not work.