COMMENT ON ​

Function Description ​

Adds a comment to a table, view, or column. The added comments can be viewed through the following system views:

• Table/View comments: MY_TAB_COMMENTS and ADM_TAB_COMMENTS

• Column comments: MY_COL_COMMENTS and ADM_COL_COMMENTS

Precautions ​

• Permission requirements:

  • No additional permissions are required to add comments to your own tables.

  • The COMMENT ANY TABLE permission is required to add comments to other users' tables.

• Supported scenarios:

  • Adding column comments during table creation is supported.

• Restrictions:

  • This operation is not supported during database restart or rollback.

Syntax ​

COMMENT ON 
{
    TABLE [ schema_name. ] { table_name | view_name }
  | COLUMN [ schema_name. ] { table_name. | view_name. } column_name
} 
IS 'string';

Parameter Description ​

• [ schema_name. ]: Username (schema name), which defaults to the currently logged-in user.

• { table_name | view_name }: Name of the table or view to which the comment is added.

• [ schema_name. ] { table_name. | view_name. } column_name: Name of the column to which the comment is added.

• IS: Keyword that specifies the comment content.

• string: Comment text, with a maximum length of 4,000 bytes.

Examples ​

-- Delete the user table user_info (if exists).
DROP TABLE IF EXISTS user_info;

-- Create a user table user_info.
CREATE TABLE user_info (user_id INT PRIMARY KEY,username VARCHAR(50) NOT NULL, email VARCHAR(100), create_time DATETIME DEFAULT CURRENT_TIMESTAMP, status CHAR(1) DEFAULT 'A');

-- Add a comment for the table user_info.
COMMENT ON TABLE user_info IS 'table of user info';

-- Add a comment for the column user_id.
COMMENT ON COLUMN user_info.user_id IS 'id of users';