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COMMENT()			 SQL Commands			     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) |
	 CAST (sourcetype AS targettype) |
	 CONSTRAINT constraint_name ON table_name |
	 CONVERSION object_name |
	 DATABASE object_name |
	 DOMAIN 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 |
	 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'


DESCRIPTION
       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  com-
       ment,  write  NULL in place of the text string.	Comments are automati-
       cally dropped when the object is dropped.

       Comments can be easily retrieved with the psql 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  and
       col_description (see the documentation).

PARAMETERS
       object_name

       table_name.column_name

       agg_name

       constraint_name

       func_name

       op

       rule_name

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

       agg_type
	      The  argument  data  type of the aggregate function, or * if the
	      function accepts any data type.

       sourcetype
	      The name of the source data type of the cast.

       targettype
	      The name of the target data type of the cast.

       argmode
	      The mode of a function argument: either IN, OUT,	or  INOUT.  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 and INOUT arguments.

       argname
	      The name of a function argument.	Note that COMMENT ON  FUNCTION
	      does  not	 actually  pay	any attention to argument names, since
	      only the argument data types are needed to determine  the	 func-
	      tion's identity.

       argtype
	      The data type(s) of the function's arguments (optionally schema-
	      qualified), if any.

       large_object_oid
	      The OID of the large object.

       PROCEDURAL
	      This is a noise word.

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

NOTES
       A comment for a database can only be created in that database, and will
       only be visible in that database, not in other databases.

       There is presently no security mechanism for comments:  any  user  con-
       nected  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.

EXAMPLES
       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 CAST (text AS int4) IS 'Allow casts from text to int4';
       COMMENT ON COLUMN my_table.my_column IS 'Employee ID number';
       COMMENT ON CONVERSION my_conv IS 'Conversion to UTF8';
       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 LANGUAGE plpython IS 'Python support for stored procedures';
       COMMENT ON LARGE OBJECT 346344 IS 'Planning document';
       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 OPERATOR CLASS int4ops USING btree IS '4 byte integer operators for btrees';
       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 RI';
       COMMENT ON TYPE complex IS 'Complex number data type';
       COMMENT ON VIEW my_view IS 'View of departmental costs';


COMPATIBILITY
       There is no COMMENT command in the SQL standard.



SQL - Language Statements	  2010-12-14			     COMMENT()
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