Defines or change the comment of an object.
COMMENT ON
{ TABLE <object_name> |
COLUMN <table_name.column_name> |
AGGREGATE <agg_name> (<agg_type> [, ...]) |
CAST (<sourcetype> AS <targettype>) |
CONSTRAINT <constraint_name> ON <table_name> |
CONVERSION <object_name> |
DATABASE <object_name> |
DOMAIN <object_name> |
FILESPACE <object_name> |
FUNCTION <func_name> ([[<argmode>] [<argname>] <argtype> [, ...]]) |
INDEX <object_name> |
LARGE OBJECT <large_object_oid> |
OPERATOR <op> (<leftoperand_type>, <rightoperand_type>) |
OPERATOR CLASS <object_name> USING <index_method> |
[PROCEDURAL] LANGUAGE <object_name> |
RESOURCE QUEUE <object_name> |
ROLE <object_name> |
RULE <rule_name> ON <table_name> |
SCHEMA <object_name> |
SEQUENCE <object_name> |
TABLESPACE <object_name> |
TRIGGER <trigger_name> ON <table_name> |
TYPE <object_name> |
VIEW <object_name> }
IS '<text>'
COMMENT
stores a comment about a database object. 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.
Comments can be easily retrieved with the psql meta-commands \dd
, \d+
, and \l+
. Other user interfaces to retrieve comments can be built atop the same built-in functions that psql uses, namely obj_description
, col_description
, and shobj_description
.
The name of the object to be commented. Names of tables, aggregates, domains, functions, indexes, operators, operator classes, sequences, types, and views may be schema-qualified.
Note: Greenplum Database does not support triggers.
*
in place of the list of input data types.
IN
,
OUT
,
INOUT
, or
VARIADIC
. If omitted, the default is
IN
. Note that
COMMENT ON FUNCTION
does not actually pay any attention to
OUT
arguments, since only the input arguments are needed to determine the function's identity. So it is sufficient to list the
IN
,
INOUT
, and
VARIADIC
arguments.
COMMENT ON FUNCTION
does not actually pay any attention to argument names, since only the argument data types are needed to determine the function's identity.
NULL
to drop the comment.
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 do not own). For shared objects such as databases, roles, and tablespaces comments are stored globally and any user connected to any database can see all the comments for shared objects. Therefore, do not put security-critical information in comments.
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;
There is no COMMENT
statement in the SQL standard.
Parent topic: SQL Command Reference