ALTER TABLE ALTER COLUMN DROP DEFAULT

Removes the default value expression from a column. INSERTs that omit the column afterward receive NULL (or fail if the column is NOT NULL).

Category: ddl

Syntax

ALTER TABLE <table> ALTER COLUMN <column> DROP DEFAULT

Description

## Overview ALTER TABLE ALTER COLUMN DROP DEFAULT removes the default expression from a column's metadata. After the drop, INSERTs that omit the column receive NULL. If the column is also NOT NULL, INSERTs that omit it fail. ## Behavior - Existing rows are not modified. Values previously inserted by the default expression remain as concrete values on disk. - DROP DEFAULT is a no-op when the column has no default. The ALTER still produces a new commit on the parent table. - The drop affects future INSERTs only. Schema-level NOT NULL constraints are unchanged; if the column is NOT NULL with no default, INSERTs that omit it now fail. ## Access Control No specific privilege is required beyond table-level access in the standalone SQL layer. ## Compatibility Standard SQL syntax.

Parameters

Name	Type	Description
`table`		Specifies the Delta table to alter.
`column_name`		Specifies the column whose default expression to remove. The column must already exist.

Examples

-- Remove the default from a status column
ALTER TABLE orders ALTER COLUMN status DROP DEFAULT;

Pitfalls

After DROP DEFAULT, INSERTs that omit a NOT NULL column raise an error. If the column was relying on the default to satisfy NOT NULL, drop NOT NULL with ALTER COLUMN DROP NOT NULL first or always supply a value at INSERT.