This is not a Mixxx issue. The QtSql.dll is missing sqlite support and you don't have a sqlite plugin available.
Did you build Qt yourself? If so, did you configure it to embed the sqlite support? If you are using the binaries from Qt, I think you will need to create a QtSQL plugin dll. I'm not sure how since I've never done it. (I build Qt myself with the embedded support and full text searching.)
This is not a Mixxx issue. The QtSql.dll is missing sqlite support and you don't have a sqlite plugin available.
Did you build Qt yourself? If so, did you configure it to embed the sqlite support? If you are using the binaries from Qt, I think you will need to create a QtSQL plugin dll. I'm not sure how since I've never done it. (I build Qt myself with the embedded support and full text searching.)