GNU/Linux man pages
Livre :
Expressions régulières,
Syntaxe et mise en oeuvre :
GNU/Linux |
CentOS 5.4 |
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comment(7) |
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COMMENT − define 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 |
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’
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 the documentation).
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.
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 function’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. |
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.
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’;
There is no COMMENT command in the SQL standard.
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comment(7) | |