@JonB
sorry for that,

insert into Dataset(AT) values(?): I know nothing about SQLite. Dataset(AT) is a (syntactically valid) table to insert into, is it?
Yes, it is valid statement in sqlite.

Also QSqlQuery::prepare() returns a bool for success/failure, which you should be checking.
Returns true if the query is prepared successfully; otherwise returns false.

Plus, you check QSqlDatabase::lastError() after QSqlQuery::exec() fails, but that says
yes, I got error. like QSqlError("","","");

I checked again there was a problem in database but it solved thanks alot.
Now, I'm able to insert data into database from QXlsx file.