table design

There is a table A as a sub-table of many functional modules, which is used to record the field changes of the main table; at the beginning, this table A designed by me has a bill_id to save the id of the main table, but one day I want to know the records of table A Which modules are the sub-tables, I can't find them, so the flaw in the design of this table is this, so I added bill_type for him to save the module's logo code and other distinguishable things