# List columns and types Shape / inspect list columns, types, metadata Page: ## Status Runs as a SQL step. arcform carries it as a `sql:` step today. ## The DuckDB step columns and types 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 column_name, column_type FROM (DESCRIBE orders); SELECT * FROM result; SELECT CASE WHEN ((SELECT count(*) = 8 AND max(column_type) FILTER (WHERE column_name = 'order_date') = 'DATE' FROM result)) THEN 'as expected' ELSE error('the schema is not eight columns with order_date a DATE') END AS verdict; ``` It needs nothing installed beyond DuckDB itself. ## Variants - [List tables and other catalog objects](https://meridian.online/operations/list-columns-and-types/list-tables-and-catalog-objects): List the databases, schemas, tables, views, functions or types a connection or session holds. - Describe a table's columns: List the name, type and other properties of each column of a table, query or stream. - Count rows and columns: Report how many rows and columns a table has. - Check that a table or column exists: Test whether a named table or column exists, as a flag or a pass or fail. - [Read a file's schema and metadata](https://meridian.online/operations/list-columns-and-types/read-a-files-schema-and-metadata): Read a data file's schema, row groups, statistics, header or detected format without loading its data. - [List keys, constraints and indexes](https://meridian.online/operations/list-columns-and-types/list-keys-constraints-and-indexes): List the keys, constraints, indexes, partitions, dependencies or relationships declared on tables. - Other metadata: Read metadata no other variant covers, such as a model's expected inputs or a dataset's descriptive information. ## What other tools call it Meridian's classification; an independent blind rating agreed on 86.2% of 312 rows (exact class, version 2). - Alteryx Designer: [`Allocate Metainfo`](https://help.alteryx.com/current/en/designer/tools/demographic-analysis/allocate-metainfo-tool.html) (read 2026-09-27) - Alteryx Designer: [`Behavior Metainfo`](https://help.alteryx.com/current/en/designer/tools/behavior-analysis/behavior-metainfo-tool.html) (read 2026-09-27) - Alteryx Designer: [`Field Info`](https://help.alteryx.com/current/en/designer/tools/developer/field-info-tool.html) (read 2026-09-27) - Apache DataFusion: [`Basic SQL Information Schema (TABLES, VIEWS, COLUMNS)`](https://datafusion.apache.org/user-guide/features.html) (read 2026-09-27) - Apache DataFusion: [`DESCRIBE`](https://datafusion.apache.org/user-guide/sql/ddl.html) (read 2026-09-27) - Apache DataFusion: [`SHOW COLUMNS FROM `](https://datafusion.apache.org/user-guide/features.html) (read 2026-09-27) - Apache DataFusion: [`SHOW CREATE TABLE `](https://datafusion.apache.org/user-guide/features.html) (read 2026-09-27) - Apache DataFusion: [`SHOW FUNCTIONS`](https://datafusion.apache.org/user-guide/sql/information_schema.html) (read 2026-09-27) - Apache DataFusion: [`SHOW TABLES`](https://datafusion.apache.org/user-guide/features.html) (read 2026-09-27) - Apache DataFusion: [`parquet_metadata`](https://datafusion.apache.org/user-guide/cli/functions.html) (read 2026-09-27) - Apache DataFusion: [`schema`](https://docs.rs/datafusion/latest/datafusion/dataframe/struct.DataFrame.html) (read 2026-09-27) - dbt-utils: [`get_filtered_columns_in_relation`](https://raw.githubusercontent.com/dbt-labs/dbt-utils/main/README.md) (read 2026-09-27) - dbt-utils: [`get_relations_by_pattern`](https://raw.githubusercontent.com/dbt-labs/dbt-utils/main/README.md) (read 2026-09-27) - dbt-utils: [`get_relations_by_prefix`](https://raw.githubusercontent.com/dbt-labs/dbt-utils/main/README.md) (read 2026-09-27) - DuckDB: [`DESCRIBE`](https://duckdb.org/docs/current/sql/statements/describe) (read 2026-09-27) - DuckDB: [`SHOW and SHOW DATABASES`](https://duckdb.org/docs/current/sql/statements/show) (read 2026-09-27) - DuckDB: `duckdb_columns` (read 2026-09-27) - DuckDB: `duckdb_constraints` (read 2026-09-27) - DuckDB: `duckdb_coordinate_systems` (read 2026-09-27) - DuckDB: `duckdb_databases` (read 2026-09-27) - DuckDB: `duckdb_dependencies` (read 2026-09-27) - DuckDB: `duckdb_indexes` (read 2026-09-27) - DuckDB: `duckdb_schemas` (read 2026-09-27) - DuckDB: `duckdb_sequences` (read 2026-09-27) - DuckDB: `duckdb_tables` (read 2026-09-27) - DuckDB: `duckdb_types` (read 2026-09-27) - DuckDB: `duckdb_views` (read 2026-09-27) - DuckDB: `parquet_bloom_probe` (read 2026-09-27) - DuckDB: `parquet_file_metadata` (read 2026-09-27) - DuckDB: `parquet_full_metadata` (read 2026-09-27) - DuckDB: `parquet_kv_metadata` (read 2026-09-27) - DuckDB: `parquet_metadata` (read 2026-09-27) - DuckDB: `parquet_schema` (read 2026-09-27) - DuckDB: `pragma_show` (read 2026-09-27) - DuckDB: `pragma_table_info` (read 2026-09-27) - Duckle: [`Describe`](https://github.com/slothflowlabs/duckle/blob/f85f8960edfb6efbf4cb89d58a7b32e16df0e867/website/docs/components.html) (read 2026-09-25) - EasyMorph: [`Table metadata`](https://help.easymorph.com/doku.php?id=transformations:metadata) (read 2026-09-27) - AWS Glue: [`printSchema`](https://docs.aws.amazon.com/glue/latest/dg/aws-glue-api-crawler-pyspark-extensions-dynamic-frame.html) (read 2026-09-27) - AWS Glue: [`schema`](https://docs.aws.amazon.com/glue/latest/dg/aws-glue-api-crawler-pyspark-extensions-dynamic-frame.html) (read 2026-09-27) - Apache Hop: [`Column exists`](https://hop.apache.org/manual/latest/pipeline/transforms/columnexists.html) (read 2026-09-27) - Apache Hop: [`Columns exist in a table`](https://hop.apache.org/manual/latest/workflow/actions/columnsexist.html) (read 2026-09-27) - Apache Hop: [`File metadata`](https://hop.apache.org/manual/latest/pipeline/transforms/filemetadata.html) (read 2026-09-27) - Apache Hop: [`Get table names`](https://hop.apache.org/manual/latest/pipeline/transforms/gettablenames.html) (read 2026-09-27) - Apache Hop: [`JDBC Metadata`](https://hop.apache.org/manual/latest/pipeline/transforms/jdbcmetadata.html) (read 2026-09-27) - Apache Hop: [`Metadata structure of stream`](https://hop.apache.org/manual/latest/pipeline/transforms/metastructure.html) (read 2026-09-27) - Apache Hop: [`Table Exists`](https://hop.apache.org/manual/latest/pipeline/transforms/tableexists.html) (read 2026-09-27) - Apache Hop: [`Table exists`](https://hop.apache.org/manual/latest/workflow/actions/tableexists.html) (read 2026-09-27) - Ibis: [`TypeOf`](https://github.com/ibis-project/ibis/blob/05d2b293344e86cb41c1a426071734f7e270335a/ibis/expr/operations/generic.py) (read 2026-09-27) - KNIME Analytics Platform: [`Column Name Extractor`](https://api.hub.knime.com/nodes/*dFOX6ADqOFSQJtqe?details=full) (read 2026-09-27) - KNIME Analytics Platform: [`DB Data Spec Extractor`](https://api.hub.knime.com/nodes/*mWe5bs8HqRo2SN9_?details=full) (read 2026-09-27) - KNIME Analytics Platform: [`Extract Color`](https://api.hub.knime.com/nodes/*CjAczqOZgMr4kuYu?details=full) (read 2026-09-27) - KNIME Analytics Platform: [`Extract Table Dimension`](https://api.hub.knime.com/nodes/*OKIm2p_-wmvT8FNf?details=full) (read 2026-09-27) - KNIME Analytics Platform: [`Extract Table Spec`](https://api.hub.knime.com/nodes/*MD6juzhoWJLJGkE9?details=full) (read 2026-09-27) - Apache NiFi: [`ExtractAvroMetadata`](https://nifi.apache.org/components/org.apache.nifi.processors.avro.ExtractAvroMetadata/) (read 2026-09-27) - Apache NiFi: [`ExtractRecordSchema`](https://nifi.apache.org/components/org.apache.nifi.processors.standard.ExtractRecordSchema/) (read 2026-09-27) - Apache NiFi: [`IdentifyMimeType`](https://nifi.apache.org/components/org.apache.nifi.processors.standard.IdentifyMimeType/) (read 2026-09-27) - Pentaho Data Integration: [`Check if a column exists`](https://docs.pentaho.com/pdia-data-integration/9.3-data-integration/pdi-transformation-steps-reference-overview) (read 2026-09-27) - Pentaho Data Integration: [`Get table names`](https://docs.pentaho.com/pdia-data-integration/9.3-data-integration/pdi-transformation-steps-reference-overview) (read 2026-09-27) - Pentaho Data Integration: [`Metadata structure of stream`](https://docs.pentaho.com/pdia-data-integration/9.3-data-integration/pdi-transformation-steps-reference-overview) (read 2026-09-27) - Pentaho Data Integration: [`Read metadata`](https://docs.pentaho.com/pdia-data-integration/9.3-data-integration/pdi-transformation-steps-reference-overview) (read 2026-09-27) - Pentaho Data Integration: [`Read metadata from Copybook`](https://docs.pentaho.com/pdia-data-integration/9.3-data-integration/pdi-transformation-steps-reference-overview) (read 2026-09-27) - Pentaho Data Integration: [`Table exists`](https://docs.pentaho.com/pdia-data-integration/9.3-data-integration/pdi-transformation-steps-reference-overview) (read 2026-09-27) - Polars: [`DataFrame attributes (family)`](https://docs.pola.rs/api/python/stable/reference/dataframe/attributes.html) (read 2026-09-27) - Polars: [`DataType expressions (group)`](https://docs.pola.rs/api/python/stable/reference/datatype_expr/index.html) (read 2026-09-27) - Polars: [`read_ipc_schema`](https://docs.pola.rs/api/python/stable/reference/io.html) (read 2026-09-27) - Polars: [`read_parquet_metadata`](https://docs.pola.rs/api/python/stable/reference/io.html) (read 2026-09-27) - Polars: [`read_parquet_schema`](https://docs.pola.rs/api/python/stable/reference/io.html) (read 2026-09-27) - Power Query M: [`Table.ColumnCount`](https://learn.microsoft.com/en-us/powerquery-m/table-functions#information) (read 2026-09-27) - Power Query M: [`Table.ColumnNames`](https://learn.microsoft.com/en-us/powerquery-m/table-functions#column-operations) (read 2026-09-27) - Power Query M: [`Table.ColumnsOfType`](https://learn.microsoft.com/en-us/powerquery-m/table-functions#column-operations) (read 2026-09-27) - Power Query M: [`Table.Keys`](https://learn.microsoft.com/en-us/powerquery-m/table-functions#transformation) (read 2026-09-27) - Power Query M: [`Table.PartitionKey`](https://learn.microsoft.com/en-us/powerquery-m/table-functions#transformation) (read 2026-09-27) - Power Query M: [`Table.PartitionValues`](https://learn.microsoft.com/en-us/powerquery-m/table-functions#information) (read 2026-09-27) - Power Query M: [`Table.Schema`](https://learn.microsoft.com/en-us/powerquery-m/table-functions#information) (read 2026-09-27) - Power Query M: [`Tables.GetRelationships`](https://learn.microsoft.com/en-us/powerquery-m/table-functions#information) (read 2026-09-27) - Apache SeaTunnel: [`TableFilter`](https://seatunnel.apache.org/docs/2.3.13/transforms/table-filter) (read 2026-09-27) - Apache SeaTunnel: [`TableRename`](https://seatunnel.apache.org/docs/2.3.13/transforms/table-rename) (read 2026-09-27) - SQLMesh: [`EXTERNAL`](https://github.com/SQLMesh/sqlmesh/blob/23b237cea7218cc8f338b89c14f0957394a0003b/docs/concepts/models/model_kinds.md) (read 2026-09-27) - subtoken: [`pragma_hnsw_index_info`](https://duckdb.org/docs/current/core_extensions/vss.html) (read 2026-09-27) - Talend: [`Database table and column list components (family)`](https://help.qlik.com/talend/en-US/components/8.0/About) (read 2026-09-27) - VisiData: [`columns-all`](https://github.com/saulpw/visidata/blob/7609212ec2febafa9caba7183cbebfaf49627909/visidata/metasheets.py#L133) (read 2026-09-23) - VisiData: [`columns-selected`](https://github.com/saulpw/visidata/blob/7609212ec2febafa9caba7183cbebfaf49627909/visidata/indexsheet.py#L102) (read 2026-09-23) - VisiData: [`columns-sheet`](https://github.com/saulpw/visidata/blob/7609212ec2febafa9caba7183cbebfaf49627909/visidata/metasheets.py#L135) (read 2026-09-23) - VisiData: [`dive-metadata`](https://github.com/saulpw/visidata/blob/7609212ec2febafa9caba7183cbebfaf49627909/visidata/loaders/hdf5.py#L87) (read 2026-09-23) - VisiData: [`sheets-all`](https://github.com/saulpw/visidata/blob/7609212ec2febafa9caba7183cbebfaf49627909/visidata/indexsheet.py#L94) (read 2026-09-23) - VisiData: [`sheets-stack`](https://github.com/saulpw/visidata/blob/7609212ec2febafa9caba7183cbebfaf49627909/visidata/indexsheet.py#L93) (read 2026-09-23) - Yggdrasil Decision Forests: [`DataSpecification`](https://github.com/google/yggdrasil-decision-forests/blob/0a54b57c95ff0cf42ecf0310ace0513a4f32cb65/yggdrasil_decision_forests/dataset/data_spec.proto) (read 2026-09-27) - Yggdrasil Decision Forests: [`Model accessors (group)`](https://github.com/google/yggdrasil-decision-forests/blob/0a54b57c95ff0cf42ecf0310ace0513a4f32cb65/yggdrasil_decision_forests/port/python/ydf/model/generic_model.py) (read 2026-09-27) - Yggdrasil Decision Forests: [`data_spec / set_data_spec`](https://github.com/google/yggdrasil-decision-forests/blob/0a54b57c95ff0cf42ecf0310ace0513a4f32cb65/yggdrasil_decision_forests/port/python/ydf/model/generic_model.py) (read 2026-09-27) - Yggdrasil Decision Forests: [`extract_input_feature_names`](https://github.com/google/yggdrasil-decision-forests/blob/0a54b57c95ff0cf42ecf0310ace0513a4f32cb65/yggdrasil_decision_forests/port/python/ydf/learner/generic_learner.py) (read 2026-09-27)