如果记录的组合不存在，则插入

Question

我有两个单独的表，一个由记录组成，另一个是组组合的主表。

Records表：

| Mobile | DC | Dept
+--------+----+------
| 123456 | 01 | car
| 098765 | 05 | home
| 123456 | 02 | taxi
| 098765 | 00 | rent

群主：

| Dept | Group-Dept
+------+-----------
| car  | Vehicle   
| taxi | Vehicle   
| home | house     
| rent | house     

预期 output：

| Mobile | DC | Dept | DC-Count | DC-Group
+--------+----+------+----------+----------
| 123456 | 01 | car  |   3      | Vehicle
| 098765 | 05 | home |   5      | house
| 123456 | 02 | taxi |   3      | Vehicle
| 098765 | 00 | rent |   5      | house

请帮忙。