add to the sql table random number

I have a table with 4 columns say

-----------------------
|data1|data2|data3|key|
-----------------------
|d1   | d2  | d3  | k1|
-----------------------
|d3   |d4   | d5  | k2|
-----------------------
|d6   | d7  | d8  | k1|
-----------------------
|d9   |d10  | d11 | k2|
-----------------------

I need to generate a new table based on this one with the same columns + id. Id should be random int64. same key should have same id For example for above table it could be :

----------------------------
|data1|data2|data3|key| id |
----------------------------
|d1   | d2  | d3  | k1|1234|
---------------------------
|d3   |d4   | d5  | k2|5678|
----------------------------
|d6   | d7  | d8  | k1|1234|
----------------------------
|d9   |d10  | d11 | k2|5678|
----------------------------

I`ll be glad to get advices