How to handle many to many relationship?

Question

I'm dealing with land development, where a land could have multiple investments and the other way around.

What I've got:

1. A shapfile with all land informations, each labels an unique id.

LAND_ID	AREA
1	100
2	1000

2. A csv file that shows how many lands involved in each cases.

CASE_ID	LANDS	INVESTOR
A01	1, 2	John
A02	2	Tom
A03	2	Dave

Solving attempts 01

First I tried to split LANDS and gave each a different rows:

CASE_ID	LANDS	INVESTOR
A01	1	John
A01	2	John
A02	2	Tom
A03	2	Dave

and join by LANDS, which...failed since QGIS seems to overwrite the same element. The output would erase row 2 & 3.

Solving attempts 02

I wrote some code outside of QGIS to make the second list looks something like this.

LAND_ID	AREA	CASES	INVESTORS
1	100	A01	John
2	1000	1.A01 ; 2.A02 ; 3.A03	1.John ; 2.Tom ; 3.Dave

So that I could join the list onto the shapfile within QGIS, yet the table becomes hard to read. I wonder if it's possible to have a 'subset-like' way to show how many investments are going on when inspecting the land? I mean by clicking on, for instance land 2, I could shows 3 tables that's related to it (in this case all of them).