Modifying Column Comments¶
Function¶
You can modify the column comments of non-partitioned or partitioned tables.
Syntax¶
ALTER TABLE [db_name.]table_name CHANGE COLUMN col_name col_name col_type COMMENT 'col_comment';
Keywords¶
CHANGE COLUMN: Modify a column.
COMMENT: column description
Parameters¶
Parameter | Mandatory | Description |
|---|---|---|
db_name | No | Database name. Only letters, digits, and underscores (_) are allowed. The name cannot contain only digits or start with an underscore (_). |
table_name | Yes | Table name |
col_name | Yes | Column name. The value must be the name of an existing column. |
col_type | Yes | Column data type specified when the table is created, which cannot be modified. |
col_comment | Yes | Column comment after modification. The comment can contain a maximum of 1024 bytes. |
Example¶
Change the comment of the c1 column in the t1 table to the new comment.
ALTER TABLE t1 CHANGE COLUMN c1 c1 STRING COMMENT 'the new comment';