Calculated field
FIRST()
Compute using: addressing Period; partitioning Region
Sample data
| Region | Period | Revenue | Cost |
|---|---|---|---|
| Harbor | 1 | 120 | 70 |
| Harbor | 2 | 180 | 100 |
| Harbor | 3 | 180 | 120 |
| Harbor | 4 | 240 | 140 |
| Upland | 1 | 90 | 50 |
| Upland | 2 | 150 | 110 |
| Upland | 3 | null | 90 |
| Upland | 4 | 330 | 190 |
The same calculation as SQL
SELECT CAST((1-row_number() OVER (PARTITION BY "Region" ORDER BY "Period" ROWS BETWEEN UNBOUNDED PRECEDING AND CURRENT ROW)) AS DOUBLE) AS result FROM input ORDER BY "Region", "Period"
Runs the example above.
SELECT CAST((1-row_number() OVER (PARTITION BY "Region" ORDER BY "Period")) AS DOUBLE) AS result FROM input ORDER BY "Region", "Period"
Written for this dialect; not run here.
SELECT CAST((1-row_number() OVER (PARTITION BY `Region` ORDER BY `Period`)) AS FLOAT64) AS result FROM input ORDER BY `Region`, `Period`
Written for this dialect; not run here.
Result
| Region | Period | Revenue | Cost | result |
|---|---|---|---|---|
| Harbor | 1 | 120 | 70 | 0 |
| Harbor | 2 | 180 | 100 | -1 |
| Harbor | 3 | 180 | 120 | -2 |
| Harbor | 4 | 240 | 140 | -3 |
| Upland | 1 | 90 | 50 | 0 |
| Upland | 2 | 150 | 110 | -1 |
| Upland | 3 | null | 90 | -2 |
| Upland | 4 | 330 | 190 | -3 |
Same rows from the calculation and from the SQL in DuckDB.
Where a naive translation goes wrong
- Omitting the region partition allows a calculation to consume marks from other regions.
Naive SQL
SELECT CAST((1-row_number() OVER ( ORDER BY "Period" ROWS BETWEEN UNBOUNDED PRECEDING AND CURRENT ROW)) AS DOUBLE) AS result FROM input ORDER BY "Region", "Period"
Region Period Revenue Cost result Harbor 1 120 70 0 Harbor 2 180 100 -2 Harbor 3 180 120 -4 Harbor 4 240 140 -6 Upland 1 90 50 -1 Upland 2 150 110 -3 Upland 3 null 90 -5 Upland 4 330 190 -7 Matches the calculation
SELECT CAST((1-row_number() OVER (PARTITION BY "Region" ORDER BY "Period" ROWS BETWEEN UNBOUNDED PRECEDING AND CURRENT ROW)) AS DOUBLE) AS result FROM input ORDER BY "Region", "Period"
Region Period Revenue Cost result Harbor 1 120 70 0 Harbor 2 180 100 -1 Harbor 3 180 120 -2 Harbor 4 240 140 -3 Upland 1 90 50 0 Upland 2 150 110 -1 Upland 3 null 90 -2 Upland 4 330 190 -3
Signature
FIRST()