问题
I have a sample code at StackBlitz that I expanded a little to include another new level Company under Address under User. It is based on the answer to a question. I like to have another nested sortable table under the Address. When a user clicks on an address row, I like to expand that row and show a table of company name, floor and unit. So far I have no luck. Appreciate if someone help me on writing the codes? Thanks
来源：https://stackoverflow.com/questions/59042625/angular-mat-table-3-level-nested-sortable-tables