The older doc [SQL Database Drivers | Qt SQL 6.7.3|https://doc.qt.io/qt-6.7/sql-driver.html#qoci-for-the-oracle-call-interface-oci] suggests the following command to build OCI plugin:
qt-cmake -G Ninja <qt_source_directory>/qtbase/src/plugins/sqldrivers -DCMAKE_INSTALL_PREFIX=<qt_installation_path>/<platform> -DOracle_INCLUDE_DIR="/usr/include/oracle/21/client64" -DOracle_LIBRARY="/usr/lib/oracle/21/client64/lib/libclntsh.<so|dylib>"
or
qt-cmake -G Ninja <qt_installation_path>\Src\qtbase\src\plugins\sqldrivers -DCMAKE_INSTALL_PREFIX=<qt_installation_path>\<platform> -DOracle_INCLUDE_DIR="C:\oracle\sdk\include" -DOracle_LIBRARY="C:\oracle\oci.lib"
and it works for both Qt 6.7 and 6.8 on both Linux and Windows. The latest doc [SQL Database Drivers | Qt SQL 6.8.0|https://doc.qt.io/qt-6/sql-driver.html#qoci-for-the-oracle-call-interface-oci] suggests
qt-cmake -G Ninja <qt_source_directory>/qtbase/src/plugins/sqldrivers -DCMAKE_INSTALL_PREFIX=<qt_installation_path>/<platform> -DOracle_ROOT="/usr/include/oracle/21/client64"
and
qt-cmake -G Ninja <qt_installation_path>\Src\qtbase\src\plugins\sqldrivers -DCMAKE_INSTALL_PREFIX=<qt_installation_path>\<platform> -DOracle_ROOT="C:\oracle"
instead. However, the "Oracle_ROOT" option does not take effects for both Qt 6.7 and 6.8 on both Linux and Windows, i.e., the cmake configuration does not build the OCI plugin at all. For example, on Linux, my Oracle instant client is placed under `/opt/oracle/instantclient_23_5" and libclntsh.<so|dylib> (all versions) files are in it. Besides, I have already added `/opt/oracle/instant_client_23_5` to `LD_LIBRARY_PATH` and `PATH`. Is it a documentation mistake or is it a new feature which does not work?