Calculated field
REGEXP_EXTRACT([label], '(birch|ash)')
Sample data
| label | quantity | amount | flag |
|---|---|---|---|
| cedar cedar | 65 | 12.8 | True |
| ORCHID-west | 66 | -7.6 | False |
| maple-east | 67 | 0 | null |
| willow north | 68 | 25.3 | True |
| birch-birch | 69 | 4.9 | False |
| pine/south | 70 | -1.2 | null |
| ash | 71 | 9 | True |
| null | null | null | null |
The same calculation as SQL
SELECT nullif(regexp_extract(label,'(birch|ash)',1),'') AS result FROM input
Runs the example above.
SELECT REGEXP_SUBSTR(label,'(birch|ash)',1,1,'e',1) AS result FROM input
Written for this dialect; not run here.
SELECT REGEXP_EXTRACT(label,r'(birch|ash)') AS result FROM input
Written for this dialect; not run here.
Result
| result |
|---|
| null |
| null |
| null |
| null |
| birch |
| null |
| ash |
| null |
Same rows from the calculation and from the SQL in DuckDB.
Where a naive translation goes wrong
- Replacing REGEXP_EXTRACT with regexp_extract(label,'(birch|ash)',1) changes the shown values or null handling.
Naive SQL
SELECT regexp_extract(label,'(birch|ash)',1) AS result FROM input
result birch ash null Matches the calculation
SELECT nullif(regexp_extract(label,'(birch|ash)',1),'') AS result FROM input
result null null null null birch null ash null
Signature
REGEXP_EXTRACT(string, constant_pattern)