> Sometime tables in a database have been locked.
> What do you think?

Are you closing the database after you are done in a finally block always? If not, do it.

>I wonder if there is any error in sql statement, the error will be thrown in catch{…} right.
Yes.

>Will the application get confused where the error should be thrown?
Software don't think so they don't get confused, we humans do :)