COMMENT

Name

COMMENT -- define or change the comment of an object

Synopsis

COMMENT ON
[
  TABLE  object_name |
  COLUMN  table_name. column_name |
  AGGREGATE  agg_name ( agg_type) |
  CONSTRAINT  constraint_name ON  table_name |
  DATABASE  object_name |
  DOMAIN  object_name |
  FUNCTION  func_name ( arg1_type,  arg2_type, ...) |
  INDEX  object_name |
  OPERATOR  op ( leftoperand_type,  rightoperand_type) |
  RULE  rule_name ON  table_name |
  SCHEMA  object_name |
  SEQUENCE  object_name |
  TRIGGER  trigger_name ON  table_name |
  TYPE  object_name |
  VIEW  object_name
] IS  'text'

Inputs

object_name, table_name.column_name, agg_name, constraint_name, func_name, op, rule_name, trigger_name

The name of the object to be be commented. Names of tables, aggregates, domains, functions, indexes, operators, sequences, types, and views may be schema-qualified.

text

The comment to add.

Outputs

COMMENT

Message returned if the table is successfully commented.

Description

COMMENT stores a comment about a database object. Comments can be easily retrieved with psql's \dd, \d+, or \l+ commands. Other user interfaces to retrieve comments can be built atop the same built-in functions that psql uses, namely obj_description() and col_description().

To modify a comment, issue a new COMMENT command for the same object. Only one comment string is stored for each object. To remove a comment, write NULL in place of the text string. Comments are automatically dropped when the object is dropped.

Note: There is presently no security mechanism for comments: any user connected to a database can see all the comments for objects in that database (although only superusers can change comments for objects that they don't own). Therefore, don't put security-critical information in comments.

Usage

Attach a comment to the table mytable:

COMMENT ON TABLE mytable IS 'This is my table.';

Remove it again:

COMMENT ON TABLE mytable IS NULL;

Some more examples:

COMMENT ON AGGREGATE my_aggregate (double precision) IS 'Computes sample variance';
COMMENT ON COLUMN my_table.my_field IS 'Employee ID number';
COMMENT ON DATABASE my_database IS 'Development Database';
COMMENT ON DOMAIN my_domain IS 'Email Address Domain';
COMMENT ON FUNCTION my_function (timestamp) IS 'Returns Roman Numeral';
COMMENT ON INDEX my_index IS 'Enforces uniqueness on employee id';
COMMENT ON OPERATOR ^ (text, text) IS 'Performs intersection of two texts';
COMMENT ON OPERATOR ^ (NONE, text) IS 'This is a prefix operator on text';
COMMENT ON RULE my_rule ON my_table IS 'Logs UPDATES of employee records';
COMMENT ON SCHEMA my_schema IS 'Departmental data';
COMMENT ON SEQUENCE my_sequence IS 'Used to generate primary keys';
COMMENT ON TABLE my_schema.my_table IS 'Employee Information';
COMMENT ON TRIGGER my_trigger ON my_table IS 'Used for R.I.';
COMMENT ON TYPE complex IS 'Complex Number datatype';
COMMENT ON VIEW my_view IS 'View of departmental costs';

Compatibility

SQL92

There is no COMMENT in SQL92.


This file was copied from PostgreSQL 7.3.1 help system.