# Add a column by condition Shape / columns if, case or switch expression to a column Page: ## Status Runs as a SQL step. arcform carries it as a `sql:` step today. ## The DuckDB step a banded column It reads the `orders` table the proofs share. Create it first: ```sql CREATE TABLE orders AS SELECT * FROM (VALUES (1, 'Alice Ng', 'north', DATE '2026-01-03', 120.00, 'widget', 'a|b', '{"channel":"web","items":[1,2]}'), (2, 'alice ng', 'north', DATE '2026-01-05', 80.50, 'gadget', 'b', '{"channel":"shop","items":[3]}'), (3, 'Bob Okafor', 'south', DATE '2026-01-05', 300.00, 'widget', 'a|c', '{"channel":"web","items":[4,5,6]}'), (4, 'Carla Díaz', 'east', DATE '2026-01-09', NULL, 'gizmo', NULL, '{"channel":"web","items":[]}'), (5, 'Bob Okafor', 'south', DATE '2026-01-12', 45.25, 'gadget', 'c', '{"channel":"phone","items":[7]}'), (6, 'Dev Patel', 'west', DATE '2026-01-12', 510.00, 'widget', 'a', '{"channel":"web","items":[8,9]}'), (7, 'Carla Diaz', 'east', DATE '2026-01-20', 99.99, 'gizmo', 'b|c', '{"channel":"shop","items":[10]}'), (8, 'Dev Patel', 'west', DATE '2026-02-02', 510.00, 'widget', 'a', '{"channel":"web","items":[8,9]}'), (9, 'Eve Larsen', NULL, DATE '2026-02-03', 15.00, 'gadget', NULL, '{"channel":"web","items":[11]}'), (10, 'Alice Ng', 'north', DATE '2026-02-10', 220.00, 'gizmo', 'a|b|c', '{"channel":"phone","items":[12,13]}') ) t(order_id, customer, region, order_date, amount, product, tags, meta); ``` Then run the statement: ```sql CREATE TEMP TABLE result AS SELECT order_id, CASE WHEN amount IS NULL THEN 'unknown' WHEN amount >= 300 THEN 'large' WHEN amount >= 100 THEN 'medium' ELSE 'small' END AS band FROM orders; SELECT * FROM result; SELECT CASE WHEN ((SELECT map_from_entries(list((band, n) ORDER BY band)) = MAP {'large': 3, 'medium': 2, 'small': 4, 'unknown': 1} FROM (SELECT band, count(*) AS n FROM result GROUP BY band))) THEN 'as expected' ELSE error('the bands do not count 3 large, 2 medium, 4 small and 1 unknown') END AS verdict; ``` It needs nothing installed beyond DuckDB itself. ## What other tools call it Meridian's classification; an independent blind rating agreed on 86.2% of 312 rows (exact class, version 2). - Azure Data Factory: [`Logical functions`](https://learn.microsoft.com/en-us/azure/data-factory/control-flow-expression-language-functions) (read 2026-09-27) - EasyMorph: [`Rule`](https://help.easymorph.com/doku.php?id=transformations:rule) (read 2026-09-27) - Ibis: [`IfElse`](https://github.com/ibis-project/ibis/blob/05d2b293344e86cb41c1a426071734f7e270335a/ibis/expr/operations/logical.py) (read 2026-09-27) - Ibis: [`SearchedCase`](https://github.com/ibis-project/ibis/blob/05d2b293344e86cb41c1a426071734f7e270335a/ibis/expr/operations/generic.py) (read 2026-09-27) - Ibis: [`SimpleCase`](https://github.com/ibis-project/ibis/blob/05d2b293344e86cb41c1a426071734f7e270335a/ibis/expr/operations/generic.py) (read 2026-09-27) - KNIME Analytics Platform: [`Column Comparator`](https://api.hub.knime.com/nodes/*vy_dP5yr5m6ZVMPE?details=full) (read 2026-09-27) - KNIME Analytics Platform: [`Rule Engine`](https://api.hub.knime.com/nodes/*zpGPAjDyExkFL2HB?details=full) (read 2026-09-27) - KNIME Analytics Platform: [`Rule Engine (Dictionary)`](https://api.hub.knime.com/nodes/*GpUdH91fJl4_KfiB?details=full) (read 2026-09-27) - KNIME Analytics Platform: [`Ruleset Editor`](https://api.hub.knime.com/nodes/*0Y5y2-u7yUx5ohSu?details=full) (read 2026-09-27) - Apache NiFi: [`Boolean Logic`](https://nifi.apache.org/nifi-docs/expression-language-guide.html) (read 2026-09-27) - OpenRefine: [`Controls`](https://openrefine.org/docs/manual/grel#controls) (read 2026-09-27) - Polars: [`SQL functions: Conditional (group)`](https://docs.pola.rs/api/python/stable/reference/sql/functions/conditional.html) (read 2026-09-27) - Polars: [`when`](https://docs.pola.rs/api/python/stable/reference/expressions/functions.html) (read 2026-09-27) - Apache SeaTunnel: [`System Functions`](https://seatunnel.apache.org/docs/2.3.13/transforms/sql-functions) (read 2026-09-27) - Tableau Prep: [`Keywords (group)`](https://help.tableau.com/current/prep/en-us/prep_function_reference.htm) (read 2026-09-27) - Tableau Prep: [`Logical functions (group)`](https://help.tableau.com/current/prep/en-us/prep_function_reference.htm) (read 2026-09-27) - Trifacta: [`Case Transform`](https://help.alteryx.com/aac/en/trifacta-classic/wrangle-language/language-appendices/transforms.html) (read 2026-09-27) - Trifacta: [`Comparison Functions (group)`](https://help.alteryx.com/aac/en/trifacta-classic/wrangle-language/comparison-functions.html) (read 2026-09-27) - Trifacta: [`Comparison Operators`](https://help.alteryx.com/aac/en/trifacta-classic/wrangle-language/comparison-functions/comparison-operators.html) (read 2026-09-27) - Trifacta: [`Conditional column`](https://help.alteryx.com/aac/en/trifacta-classic/reference/transformation-reference.html) (read 2026-09-27) - Trifacta: [`Logical Functions (group)`](https://help.alteryx.com/aac/en/trifacta-classic/wrangle-language/logical-functions.html) (read 2026-09-27) - Trifacta: [`Logical Operators`](https://help.alteryx.com/aac/en/trifacta-classic/wrangle-language/logical-functions/logical-operators.html) (read 2026-09-27) - Trifacta: [`Ternary Operators`](https://help.alteryx.com/aac/en/trifacta-classic/wrangle-language/other-functions/ternary-operators.html) (read 2026-09-27)