# Split a list into rows Shape / rows one row to many: unnest, explode, split to rows Page: ## Status Runs as a SQL step. arcform carries it as a `sql:` step today. ## The DuckDB step split a delimited column to rows 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, unnest(string_split(tags, '|')) AS tag FROM orders WHERE tags IS NOT NULL; SELECT * FROM result; SELECT CASE WHEN ((SELECT count(*) = 13 AND count(*) FILTER (WHERE order_id = 10) = 3 FROM result)) THEN 'as expected' ELSE error('the tags did not expand to 13 rows with three for order 10') END AS verdict; ``` It needs nothing installed beyond DuckDB itself. ## Variants - Keep rows whose list is empty: Unnest while keeping a row with a null element where the list is null or empty. - Flatten nested records into rows: Expand nested tables, record sets, XML or graph values into rows and columns of their own. - Other ways to make more rows: Insert rows for gaps, chunk text or map one row onto several. - [Repeat each row](https://meridian.online/operations/split-a-list-into-rows/repeat-each-row): Emit several copies of each row, a set or column-given number of times or along a generated sequence. - [Split delimited text into rows](https://meridian.online/operations/split-a-list-into-rows/split-delimited-text-into-rows): Split a text value on a separator or pattern and emit one row per item. - Turn each list element into a row: Emit one row per element of a list, array or JSON array column, repeating the other columns. ## 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: [`Flatten`](https://learn.microsoft.com/en-us/azure/data-factory/data-flow-flatten) (read 2026-09-27) - Alteryx Designer: [`Generate Rows`](https://help.alteryx.com/current/en/designer/tools/preparation/generate-rows-tool.html) (read 2026-09-27) - Apache DataFusion: [`UNNEST`](https://datafusion.apache.org/user-guide/sql/select.html) (read 2026-09-27) - Apache DataFusion: [`unnest`](https://datafusion.apache.org/user-guide/sql/special_functions.html) (read 2026-09-27) - Apache DataFusion: [`unnest_columns`](https://docs.rs/datafusion/latest/datafusion/dataframe/struct.DataFrame.html) (read 2026-09-27) - Apache DataFusion: [`unnest_outer`](https://datafusion.apache.org/user-guide/sql/select.html) (read 2026-09-27) - DuckDB: [`Unnesting (clause)`](https://duckdb.org/docs/current/sql/query_syntax/unnest) (read 2026-09-27) - DuckDB: `unnest` (read 2026-09-27) - Duckle: [`Explode / Unnest`](https://github.com/slothflowlabs/duckle/blob/f85f8960edfb6efbf4cb89d58a7b32e16df0e867/website/docs/components.html) (read 2026-09-25) - Duckle: [`Normalize`](https://github.com/slothflowlabs/duckle/blob/f85f8960edfb6efbf4cb89d58a7b32e16df0e867/website/docs/components.html) (read 2026-09-25) - Duckle: [`Zip Arrays to Table`](https://github.com/slothflowlabs/duckle/blob/f85f8960edfb6efbf4cb89d58a7b32e16df0e867/frontend/src/workflow-ui/palette-data.ts) (read 2026-09-25) - EasyMorph: [`Repeat rows`](https://help.easymorph.com/doku.php?id=transformations:repeatrows) (read 2026-09-27) - EasyMorph: [`Split JSON array`](https://help.easymorph.com/doku.php?id=transformations:splitjsonarray) (read 2026-09-27) - EasyMorph: [`Split delimited text into rows`](https://help.easymorph.com/doku.php?id=transformations:subfield) (read 2026-09-27) - AWS Glue: [`Explode Array or Map Into Rows`](https://docs.aws.amazon.com/glue/latest/dg/transforms-explode-array.html) (read 2026-09-27) - AWS Glue: [`Relationalize`](https://docs.aws.amazon.com/glue/latest/dg/aws-glue-api-crawler-pyspark-transforms-Relationalize.html) (read 2026-09-27) - Apache Hop: [`Clone row`](https://hop.apache.org/manual/latest/pipeline/transforms/clonerow.html) (read 2026-09-27) - Apache Hop: [`Neo4j split graph`](https://hop.apache.org/manual/latest/pipeline/transforms/neo4j-split-graph.html) (read 2026-09-27) - Apache Hop: [`Split fields to rows`](https://hop.apache.org/manual/latest/pipeline/transforms/splitfieldtorows.html) (read 2026-09-27) - Ibis: [`TableUnnest`](https://github.com/ibis-project/ibis/blob/05d2b293344e86cb41c1a426071734f7e270335a/ibis/expr/operations/relations.py) (read 2026-09-27) - Ibis: [`Unnest`](https://github.com/ibis-project/ibis/blob/05d2b293344e86cb41c1a426071734f7e270335a/ibis/expr/operations/arrays.py) (read 2026-09-27) - KNIME Analytics Platform: [`Ungroup`](https://api.hub.knime.com/nodes/*aItro4n6xSMUuxg-?details=full) (read 2026-09-27) - Apache NiFi: [`ForkRecord`](https://nifi.apache.org/components/org.apache.nifi.processors.standard.ForkRecord/) (read 2026-09-27) - Apache NiFi: [`SplitJson`](https://nifi.apache.org/components/org.apache.nifi.processors.standard.SplitJson/) (read 2026-09-27) - Apache NiFi: [`SplitXml`](https://nifi.apache.org/components/org.apache.nifi.processors.standard.SplitXml/) (read 2026-09-27) - OpenRefine: [`Split multi-valued cells…`](https://openrefine.org/docs/manual/cellediting#split-multi-valued-cells) (read 2026-09-27) - Pentaho Data Integration: [`Clone row`](https://docs.pentaho.com/pdia-data-integration/9.3-data-integration/pdi-transformation-steps-reference-overview) (read 2026-09-27) - Pentaho Data Integration: [`Split field to rows`](https://docs.pentaho.com/pdia-data-integration/9.3-data-integration/pdi-transformation-steps-reference-overview) (read 2026-09-27) - Polars: [`DataFrame.explode`](https://docs.pola.rs/api/python/stable/reference/dataframe/modify_select.html) (read 2026-09-27) - Polars: [`Expr manipulation/selection: expansion and reshaping (group)`](https://docs.pola.rs/api/python/stable/reference/expressions/modify_select.html) (read 2026-09-27) - Power Query M: [`Table.ExpandListColumn`](https://learn.microsoft.com/en-us/powerquery-m/table-functions#transformation) (read 2026-09-27) - Power Query M: [`Table.ExpandTableColumn`](https://learn.microsoft.com/en-us/powerquery-m/table-functions#transformation) (read 2026-09-27) - Power Query M: [`Table.Repeat`](https://learn.microsoft.com/en-us/powerquery-m/table-functions#row-operations) (read 2026-09-27) - RapidMiner Studio: [`Fill Data Gaps`](https://docs.rapidminer.com/latest/studio/operators/cleansing/missing/fill_data_gaps.html) (read 2026-09-27) - Apache SeaTunnel: [`LATERAL VIEW EXPLODE`](https://seatunnel.apache.org/docs/2.3.13/transforms/sql-functions) (read 2026-09-27) - Apache SeaTunnel: [`TextChunk`](https://seatunnel.apache.org/docs/transforms/text-chunk) (read 2026-09-27) - Talend: [`tDuplicateRow`](https://help.qlik.com/talend/en-US/components/8.0/data-privacy/data-privacy-component) (read 2026-09-27) - Talend: [`tNormalize`](https://help.qlik.com/talend/en-US/components/8.0/processing/processing-component) (read 2026-09-27) - Talend: [`tParseRecordSet`](https://help.qlik.com/talend/en-US/components/8.0/db-generic/db-generic-component) (read 2026-09-27) - Talend: [`tSplitRow`](https://help.qlik.com/talend/en-US/components/8.0/processing/processing-component) (read 2026-09-27) - Trifacta: [`Expand Array to rows`](https://help.alteryx.com/aac/en/trifacta-classic/reference/transformation-reference.html) (read 2026-09-27) - Trifacta: [`Flatten Transform`](https://help.alteryx.com/aac/en/trifacta-classic/wrangle-language/language-appendices/transforms.html) (read 2026-09-27) - Trifacta: [`Split into rows`](https://help.alteryx.com/aac/en/trifacta-classic/reference/transformation-reference.html) (read 2026-09-27) - Trifacta: [`Splitrows Transform`](https://help.alteryx.com/aac/en/trifacta-classic/wrangle-language/language-appendices/transforms.html) (read 2026-09-27) - VisiData: [`unfurl-col`](https://github.com/saulpw/visidata/blob/7609212ec2febafa9caba7183cbebfaf49627909/visidata/features/unfurl.py#L69) (read 2026-09-23)