I want to concatenate some fields in one string with comma as a delimeter, but want to omit the values that are blank.

MyDE
| UNIQUE_ID | BLOCK_ID1 | BLOCK_ID2 |
|:---- |:------:| -----:|
| A  | 1   | 2 |
| B  | 1   | 2 |
| C  | 1   |  |

When i do:
````
SELECT UNIQUE_ID,
CONCAT(BLOCK_ID1,', ', BLOCK_ID2) as BLOCK_ID
From My DE
````
OUTPUT DE:
| UNIQUE_ID | BLOCK_ID |
|:---- |:------:|
| A  | 1, 2,    |
| B  | 1, 2,    |
| C  | 1,   |

I want to remove the last comma from my output DE