An MSVC debug-and-release build of Qt with the MySQL plugin requires separate builds of the MySQL client library: a debug and a release build. There was no way to specify the debug version of the library. Now, it's possible to configure Qt like this: cmake ... \ -DMySQL_ROOT=D:\mysql-connector-c-6.1.11-winx64 \ -DMySQL_LIBRARY_DIR=D:\mysql-connector-c-6.1.11-winx64\lib\vs14 This will automatically detect the include dir and the debug and release library files. We expect that the debug build of the MySQL client library resides in a "debug" subdirectory below MySQL_LIBRARY_DIR. If the automatic detection doesn't work to due a different layout on the build machine, one can set the variable MySQL_LIBRARY_DEBUG to specify the debug variant of the MySQL client library. [ChangeLog][CMake] If pkg-config is not used, a debug build of the MySQL client library can be specified with -DMySQL_LIBRARY_DEBUG=<path-to-library>. The debug and release variants of the library are automatically detected. Setting MySQL_ROOT and MySQL_LIBRARY_DIR is sufficient in most cases. Pick-to: 6.2 6.4 Task-number: QTQAINFRA-4999 Change-Id: I663fb8ac1dbd07bc73484791be9cc21bff2f4a9b Reviewed-by: Edward Welbourne <edward.welbourne@qt.io> Reviewed-by: Amir Masoud Abdol <amir.abdol@qt.io> Reviewed-by: Alexey Edelev <alexey.edelev@qt.io>