Qt doesn't load any database drivers - mysql

Question

I'm porting my project from qt4.8.4 on windows server 2003(32bit) to qt5.3.1 on win7(64bit), I build qt source statically, and build qsqlmysql dynamically, but my code can not load mysql qt driver. The error is like follows,
QSqlDatabase: QMYSQL driver not loaded
QSqlDatabase: available drivers:()
My code is as follows,
db = QSqlDatabase::addDatabase("QMYSQL", "*****");
db.setHostName("*****");
db.setDatabaseName("*****");
db.setUserName("*****");
db.setPassword("*****");
When I search "QMYSQL" in registry, I get nothing, it seems qmysql driver is not registered.
Any ideas?

Answer 1

A default configuration will only give you sqlite support, maybe ODBC will be auto-detected on windows. You will need to specify sql support and possibly provide libs and include paths too. For example (using mardiadbclient for mysql):
Pre Qt 5.8:
-qt-sql-mysql -L E:\msys64\mingw64\lib -l mysqlclient -I E:\msys64\mingw64\include\mariadb
Post Qt 5.8:
-sql-mysql MYSQL_INCDIR=E:\msys64\mingw64\include\mariadb MYSQL_LIBDIR=E:\msys64\mingw64\lib MYSQL_LIBS="-l mysqlclient" -L
E:\msys64\mingw64\lib

Answer 2

in qt4.8.4, when you link qsqlmysql statically, you should write:
Q_IMPORT_PLUGIN(qsqlmysql)
but in qt5.3.1, the name changed, you should write the macro as following:
Q_IMPORT_PLUGIN(QMYSQLDriverPlugin)
That's why i always get a unresolved external... error. After change the name, i can link mysql successfully.