各位先進，小弟之前在 Delphi10 用 Universal Data Access Components (UniDAC) 相關元件連結遠端的 Mysql 資料庫，發佈到客端也都能正常使用，但現在發佈到 Windows 7/8 X64 下卻發生 『類別未登錄』(Class not registered) 的錯誤，我嘗試使用 libmysql.dll 並註冊，也都沒有效果，不堪其擾，故此，請有使用經驗的先進，能夠不吝提點，謝謝。

MySQL Connectivity Aspects

Client mode:
If you are developing a 64-bit application, you have to be aware of specifics of working with client libraries at design-time and run-time. To connect to a MySQL database at design-time, you must have its 32-bit client library. You have to place it to the C:\Windows\SysWOW64 directory. This requirement flows out from the fact that RAD Studio XE2 is a 32-bit application and it cannot load 64-bit libraries at design-time. To work with a MySQL database in run-time (64-bit application), you must have the 64-bit client library placed to the C:\Windows\System32 directory.
DIRECT mode:
Since there is no need to install client library for the DIRECT mode, the specifics of developing applications that use UniDAC as data access components, depends exclusively on peculiarities of each target platform.


===================引 用 pcernet 文 章===================
各位先進，小弟之前在 Delphi10 用 Universal Data Access Components (UniDAC) 相關元件連結遠端的 Mysql 資料庫，發佈到客端也都能正常使用，但現在發佈到 Windows 7/8 X64 下卻發生 『類別未登錄』(Class not registered) 的錯誤，我嘗試使用 libmysql.dll 並註冊，也都沒有效果，不堪其擾，故此，請有使用經驗的先進，能夠不吝提點，謝謝。

一直都在使用UniDAC,
沒有發生過你提的問題,
文件中是有提到必須放一顆元件, "TMySQLUniProvider"在Form上面,
一個Application只要放一次即可,
Client端並不需要安裝任何的MySQL DLLs

在connection中的OPtions中选择直联，就不用带相应的DLL了