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 in place of the text string. Comments are automatically deleted when their objects are deleted.
• Currently, there is no security protection for viewing comments. Any user connected to a database can view all the comments for objects in the database. For shared objects such as databases, roles, and tablespaces, comments are stored globally so any user connected to any database in the cluster can see all the comments for shared objects. Therefore, do not put security-critical information in comments.
• For most kinds of objects, only the owner of objects can set the comment. Roles do not have owners, so the rule for COMMENT ON ROLE is that you must be administrator to comment on an administrator role, or have the CREATE ROLE permission to comment on non-administrator roles. An administrator 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

• agg_name

  Specifies the new name of an aggregation function.

• 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 the object to be commented.

• 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.

• table_name

  Specifies the table name.

• function_name

  Specifies the function whose comment is defined or modified.

• 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

  The data type(s) of the operator's arguments (optionally schema-qualified). Write NONE for the missing argument of a prefix or postfix operator.

• text

  Specifies the new comment, written as a string literal; or NULL to drop the comment.

Examples

Create a 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);

Add a comment to the customer.c_customer_sk column.

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

Create a view

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CREATE OR REPLACE VIEW customer_details_view AS SELECT * FROM CUSTOMER;

Add a comment to the customer_details_view view:

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COMMENT ON VIEW customer_details_view IS 'View of customer detail';

Add a comment to the customer table.

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COMMENT ON TABLE customer IS 'This is my table';