Help Center/ MapReduce Service/ Component Operation Guide (LTS)/ Using Hudi/ Hudi Schema Evolution/ Hudi Schema Evolution and Syntax/ ALTER COLUMN
Updated on 2026-06-27 GMT+08:00
View PDF
Share

ALTER COLUMN

Function

The ALTER TABLE ... ALTER COLUMN command is used to change the attributes of a column, such as the column type and position.

Syntax

ALTER TABLE Table name ALTER

[COLUMN] col_old_name TYPE column_type

[FIRST|AFTER] column_name

Parameter Description

Table 1 ALTER COLUMN parameters

Parameter

Description

tableName

Table name.

col_old_name

Name of the column to be altered.

column_type

Type of the target column.

column_name

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

Example

  • Changing the column type 
    ALTER TABLE table1 ALTER COLUMN a.b.c TYPE bigint

    a.b.c indicates the full path of a nested column. For details about the nested column rules, see ADD COLUMNS.

    The following changes on column types are supported:

    • int => long/float/double/string/decimal
    • long => float/double/string/decimal
    • float => double/String/decimal
    • From double to string or decimal
    • From decimal to decimal or string
    • From string to date or decimal
    • From date to string
  • Altering other attributes 
    ALTER TABLE table1 ALTER COLUMN a.b.c DROP NOT NULL
ALTER TABLE table1 ALTER COLUMN a.b.c FIRST
ALTER TABLE table1 ALTER COLUMN a.b.c AFTER x

    a.b.c indicates the full path of a nested column. For details about the nested column rules, see ADD COLUMNS.

Response

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