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 (arg1_type, arg2_type, ...) | 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 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 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 Table 9-43).
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, aggregates, 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.
- large_object_oid
The OID of the large object.
- PROCEDURAL
This is a noise word.
- sourcetype
The name of the source data type of the cast.
- targettype
The name of the target data type of the cast.
- 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 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.
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 Unicode';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.
