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| src__id | period | amount_a | amount_b | amount_c | A+B-C |
|---|---|---|---|---|---|
| id1 | Q1 | 2 | 9 | null | 11 |
| id2 | Q2 | null | 1 | 4 | -3 |
SELECT 2
| src__id | period | amount_a | amount_b | amount_c | A+B-C |
|---|---|---|---|---|---|
| id1 | Q1 | 2 | 9 | 0 | 11 |
| id2 | Q2 | 0 | 1 | 4 | -3 |
SELECT 2