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'
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.
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';