Small differences between ibatis variables # And $

This morning, I helped my colleague solve a problem. He wanted to use the table name as a parameter.

For example

Select * from # tablename #

The result shows no. When an error is reported in the background, the # defined parameter is equivalent to select * from? Then pass the parameter. Obviously, this is not the case,
Change

Select * from $ tablename $
Okay, it seems that using $ is a simple replacement. In fact, I didn't pay attention to it before # The difference with $, huh, huh.

I sent it up without careful research. If you have any questions, please correct them.