Help Center/ Data Lake Insight/ Delta SQL Syntax Reference/ Delta SQL Syntax Reference/ Schema Evolution Syntax/ ALTER COLUMN
Updated on 2025-04-21 GMT+08:00
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ALTER COLUMN

Function

This syntax modifies the current column properties, including column comments and null constraints. Currently, it does not support modifying column types or column positions.

Precautions

  • Modifying column types is currently not supported.
  • Modifying the order of existing columns is currently not supported.
  • Adding columns in a specified order is currently not supported.

Syntax

ALTER TABLE Table name ALTER

[COLUMN] col_name

[COMMENT] col_comment

Parameter Description

Table 1 ALTER COLUMN parameters

Parameter

Description

tableName

Table name.

col_name

Name of the column to be altered.

column_type

Type of the target column.

col_comment

Column comment.

column_name

New position to place the target column. For example, AFTER column_name indicates that the target column is placed after column_name.

Required Permissions

  • SQL permissions
Table 2 Permissions required for executing ALTER TABLE

Permission Description

ALTER permission on a table
  • Fine-grained permission: dli:table:alter
  • Metadata services provided by LakeFormation. Refer to the LakeFormation documentation for details on permission configuration.

Example

  • Altering other attributes 
    ALTER TABLE table1 ALTER COLUMN col_a DROP NOT NULL

ALTER TABLE table1 ALTER COLUMN col_a COMMENT 'new comment'

Response

You can run the DESCRIBE command to view the modified column.

Parent topic: Schema Evolution Syntax