+----+------+
| id | name |
+----+------+
| 1  | Bob  |
+----+------+
| 2  | Alice|
+----+------+
| 3  | John |
+----+------+

+----+--------+
| id |  name  |
+----+--------+
| 1  | Group 1|
+----+--------+
| 2  | Group 2|
+----+--------+
| 3  | Group 3|
+----+--------+

+-------------+------------------+
| customer_id | customergroup_id |
+-------------+------------------+
|  1          |   1              |
+-------------+------------------+
|  1          |   3              |
+-------------+------------------+
|  2          |   2              |
+-------------+------------------+

+----+------------+
| id |  name      |
+----+------------+
| 1  | Wristwatch |
+----+------------+
| 2  | Tank top   |
+----+------------+
| 3  | Sneakers   |
+----+------------+
| 4  | Sweatshirt |
+----+------------+

+------------+------------------+
| product_id | customergroup_id |
+------------+------------------+
|  1         |   1              |
+------------+------------------+
|  1         |   2              |
+------------+------------------+
|  4         |   1              |
+------------+------------------+
|  2         |   3              |
+------------+------------------+
|  3         |   1              |
+------------+------------------+
|  3         |   3              |
+------------+------------------+