Help Center/ GaussDB(DWS)/ SQL Syntax Reference/ SQL Syntax Reference (9.1.0.x)/ DDL Syntax/ COMMENT
Updated on 2025-07-22 GMT+08:00
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COMMENT

Function

COMMENT defines or changes the comment of an object.

Precautions

  • Only one comment string is stored for each object. To modify a comment, issue a new COMMENT command for the same object. To remove a comment, write NULL at the location of the text string. Comments are automatically deleted when their objects are deleted.
  • There is no security for viewing comments. Any user with database access can see all object comments. Comments on shared items like databases, roles, and tablespaces are visible to any user connected to any database in the cluster. Avoid adding sensitive security information to comments.
  • For most objects, only the owner of the object can set comments. A role has no owner. So, only a system admin can use the COMMENT ON ROLE command for system admin roles. Roles with the CREATE ROLE permission can add comments to non-admin roles. Administrators can comment on anything.

Syntax

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COMMENT ON
{
  AGGREGATE agg_name (agg_type [, ...] ) |
  CAST (source_type AS target_type) |
  COLLATION object_name |
  COLUMN { table_name.column_name | view_name.column_name } |
  CONSTRAINT constraint_name ON table_name |
  CONVERSION object_name |
  DATABASE object_name |
  DOMAIN object_name |
  EXTENSION object_name |
  FOREIGN DATA WRAPPER object_name |
  FOREIGN TABLE object_name |
  FUNCTION function_name ( [ {[ argmode ] [ argname ] argtype} [, ...] ] ) |
  INDEX object_name |
  LARGE OBJECT large_object_oid |
  OPERATOR operator_name (left_type, right_type) |
  OPERATOR CLASS object_name USING index_method |
  OPERATOR FAMILY object_name USING index_method |
  [ PROCEDURAL ] LANGUAGE object_name |
  ROLE object_name |
  RULE rule_name ON table_name |
  SCHEMA object_name |
  SERVER object_name |
  TABLE object_name |
  TABLESPACE object_name |
  TEXT SEARCH CONFIGURATION object_name |
  TEXT SEARCH DICTIONARY object_name |
  TEXT SEARCH PARSER object_name |
  TEXT SEARCH TEMPLATE object_name |
  TYPE object_name |
  VIEW object_name
}
   IS 'text';

Parameter Description

Table 1 COMMENT parameters

Parameter

Description

Value Range

agg_name

Specifies the name of the aggregate function to be commented out.

-

agg_type

Specifies the data types of the aggregation function parameters.

-

source_type

Specifies the name of the source data type of the cast.

-

target_type

Specifies the name of the target data type of the cast.

-

object_name

Specifies the name of an object.

-

table_name.column_name/view_name.column_name

Specifies the column whose comment is defined or modified. You can add the table name or view name as the prefix.

-

constraint_name

Specifies the table constraints whose comment is defined or modified.

Name of an existing table constraint.

table_name

Specifies the table name.

Name of an existing table.

function_name

Specifies the function whose comment is defined or modified.

Use an existing function name.

argmode/argname/argtype

Specifies the schema, name, and type of the function parameters.

-

large_object_oid

Specifies the OID of the large object whose comment is defined or modified.

-

operator_name

Specifies the name of the operator.

-

left_type/right_type

Specifies the data type of the operation parameter, which can be specified by a pattern. Write NONE for the missing argument of a prefix or postfix operator.

-

text

Specifies the new comment.

A string.

Examples

Create a sample table CUSTOMER and add comments to the customer.c_customer_sk column of the table.

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CREATE TABLE IF NOT EXISTS CUSTOMER
(    
    C_CUSTKEY     BIGINT NOT NULL CONSTRAINT C_CUSTKEY_pk PRIMARY KEY  , 
    C_NAME        VARCHAR(25)  , 
    C_ADDRESS     VARCHAR(40)  , 
    C_NATIONKEY   INT          , 
    C_PHONE       CHAR(15)     , 
    C_ACCTBAL     DECIMAL(15,2)  
)
DISTRIBUTE BY HASH(C_CUSTKEY);

COMMENT ON COLUMN customer.c_customer_sk IS 'Primary key of customer demographics table.';

Create the customer_details_view view and add comments to the view.

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CREATE OR REPLACE VIEW customer_details_view AS SELECT * FROM CUSTOMER;
COMMENT ON VIEW customer_details_view_v2 IS 'View of customer detail';

Add comments to the customer table.

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COMMENT ON TABLE customer IS 'This is my table';
Parent Topic: DDL Syntax