Table Operations

.. list-table:: :header-rows: 1 :widths: 20 60

• • Function
  • Description
• • :ref:CREATE TABLE <create_table>
  • Create a new table and its columns from a SQL query executed against an existing table.
• • :ref:DELETE FROM <delete_from_table>
  • Remove specific rows of data from a table using an (optional) constraint.
• • :ref:DROP TABLES <drop_tables>
  • Deletes the specified table, unregistering it.
• • :ref:EXPLAIN <explain>
  • Returns the Polars execution plan for a given SQL query.
• • :ref:SHOW TABLES <show_tables>
  • Returns a list of all tables registered in the given context.
• • :ref:UNNEST <unnest_table_func>
  • Unnest one or more arrays as columns in a new table object.
• • :ref:TRUNCATE <truncate>
  • Remove all data from a table without actually deleting it.

.. _create_table:

CREATE TABLE

Create a new table from a sequence of column definitions, a SQL query executed against an existing table, or create an empty table from the schema of an existing table.

Example:

.. code-block:: sql

CREATE TABLE tbl(colx VARCHAR, coly DATE, colz ARRAY<DOUBLE>)

.. code-block:: sql

CREATE TABLE new_table AS
SELECT * FROM existing_table WHERE value > 42

.. code-block:: sql

CREATE TABLE new_table LIKE existing_table

.. _delete_from_table:

DELETE

Remove specific rows from a table using an (optional) constraint. Omitting the constraint deletes all rows, equivalent to TRUNCATE.

Example:

.. code-block:: sql

DELETE FROM some_table WHERE value < 0

.. _drop_tables:

DROP TABLES

Deletes the specified table, unregistering it.

Example:

.. code-block:: sql

DROP TABLE old_table

.. _explain:

EXPLAIN

Returns the Polars execution plan for a given SQL query.

Example:

.. code-block:: sql

EXPLAIN SELECT * FROM some_table

.. _show_tables:

SHOW TABLES

Returns a list of all tables registered in the given context.

Example:

.. code-block:: sql

SHOW TABLES

.. _unnest_table_func:

UNNEST

Unnest one or more arrays as columns in a new table object.

Example:

.. code-block:: sql

SELECT * FROM
  UNNEST(
    [1, 2, 3, 4],
    ['ww','xx','yy','zz'],
    [23.0, 24.5, 28.0, 27.5]
  ) AS tbl (x,y,z)

.. _truncate:

TRUNCATE

Remove all data from a table without deleting the table itself.

Example:

.. code-block:: sql

TRUNCATE TABLE some_table