COMMENT — 定義或更改物件的註釋
COMMENT ON
{
ACCESS METHOD object_name |
AGGREGATE aggregate_name ( aggregate_signature ) |
CAST (source_type AS target_type) |
COLLATION object_name |
COLUMN relation_name.column_name |
CONSTRAINT constraint_name ON table_name |
CONSTRAINT constraint_name ON DOMAIN domain_name |
CONVERSION object_name |
DATABASE object_name |
DOMAIN object_name |
EXTENSION object_name |
EVENT TRIGGER object_name |
FOREIGN DATA WRAPPER object_name |
FOREIGN TABLE object_name |
FUNCTION function_name [ ( [ [ argmode ] [ argname ] argtype [, ...] ] ) ] |
INDEX object_name |
LARGE OBJECT large_object_oid |
MATERIALIZED VIEW object_name |
OPERATOR operator_name (left_type, right_type) |
OPERATOR CLASS object_name USING index_method |
OPERATOR FAMILY object_name USING index_method |
POLICY policy_name ON table_name |
[ PROCEDURAL ] LANGUAGE object_name |
PROCEDURE procedure_name [ ( [ [ argmode ] [ argname ] argtype [, ...] ] ) ] |
PUBLICATION object_name |
ROLE object_name |
ROUTINE routine_name [ ( [ [ argmode ] [ argname ] argtype [, ...] ] ) ] |
RULE rule_name ON table_name |
SCHEMA object_name |
SEQUENCE object_name |
SERVER object_name |
STATISTICS object_name |
SUBSCRIPTION object_name |
TABLE object_name |
TABLESPACE object_name |
TEXT SEARCH CONFIGURATION object_name |
TEXT SEARCH DICTIONARY object_name |
TEXT SEARCH PARSER object_name |
TEXT SEARCH TEMPLATE object_name |
TRANSFORM FOR type_name LANGUAGE lang_name |
TRIGGER trigger_name ON table_name |
TYPE object_name |
VIEW object_name
} IS { string_literal | NULL }
where aggregate_signature is:
* |
[ argmode ] [ argname ] argtype [ , ... ] |
[ [ argmode ] [ argname ] argtype [ , ... ] ] ORDER BY [ argmode ] [ argname ] argtype [ , ... ]
COMMENT 儲存有關資料庫物件的註釋。
每個物件只儲存一個註釋字串，因此要修改註釋，請為同一物件發出新的 COMMENT 命令。要刪除註釋，請在文字字串的位置寫 NULL。當其物件被刪除時，註釋會自動刪除。
將獲取對要註釋的物件 SHARE UPDATE EXCLUSIVE 鎖。
對於大多數型別的物件，只有物件的擁有者才能設定註釋。角色沒有擁有者，因此 COMMENT ON ROLE 的規則是，您必須是超級使用者才能註釋超級使用者角色，或者擁有 CREATEROLE 許可權，並被授予目標角色的 ADMIN OPTION。同樣，訪問方法也沒有擁有者；您必須是超級使用者才能註釋訪問方法。當然，超級使用者可以註釋任何內容。
可以使用 psql 的 \d 系列命令檢視註釋。用於檢索註釋的其他使用者介面可以構建在 psql 使用的相同內建函式之上，即 obj_description、col_description 和 shobj_description（請參閱 表 9.82）。
object_namerelation_name.column_nameaggregate_nameconstraint_namefunction_nameoperator_namepolicy_nameprocedure_nameroutine_namerule_nametrigger_name要註釋的物件的名稱。位於模式中的物件（表、函式等）的名稱可以被模式限定。註釋列時，relation_name 必須引用表、檢視、複合型別或外部表。
table_namedomain_name在建立約束、觸發器、規則或策略的註釋時，這些引數指定了定義該物件的表或域的名稱。
source_type型別轉換的源資料型別的名稱。
target_type型別轉換的目標資料型別的名稱。
argmode函式、過程或聚合引數的模式： IN、OUT、INOUT 或 VARIADIC。如果省略，則預設為 IN。請注意，COMMENT 實際上並不關注 OUT 引數，因為只有輸入引數才能確定函式的標識。因此，列出 IN、INOUT 和 VARIADIC 引數就足夠了。
argname函式、過程或聚合引數的名稱。請注意，COMMENT 實際上並不關注引數名稱，因為只有引數資料型別才能確定函式的標識。
argtype函式、過程或聚合引數的資料型別。
large_object_oid大物件的 OID。
left_typeright_type運算子引數的資料型別（可選模式限定）。對於字首運算子的缺失引數，請寫 NONE。
PROCEDURAL這是一個噪聲詞。
type_name轉換的資料型別的名稱。
lang_name轉換的語言的名稱。
string_literal新的註釋內容，以字串字面量表示。
NULL寫 NULL 以刪除註釋。
目前沒有檢視註釋的安全機制：連線到資料庫的任何使用者都可以看到該資料庫中所有物件的註釋。對於共享物件（如資料庫、角色和表空間），註釋是全域性儲存的，因此連線到叢集中任何資料庫的任何使用者都可以看到所有共享物件的註釋。因此，請勿在註釋中放置安全敏感資訊。
為表 mytable 添加註釋
COMMENT ON TABLE mytable IS 'This is my table.';
再次移除它
COMMENT ON TABLE mytable IS NULL;
更多示例
COMMENT ON ACCESS METHOD gin IS 'GIN index access method'; 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 COLLATION "fr_CA" IS 'Canadian French'; COMMENT ON COLUMN my_table.my_column IS 'Employee ID number'; COMMENT ON CONVERSION my_conv IS 'Conversion to UTF8'; COMMENT ON CONSTRAINT bar_col_cons ON bar IS 'Constrains column col'; COMMENT ON CONSTRAINT dom_col_constr ON DOMAIN dom IS 'Constrains col of domain'; COMMENT ON DATABASE my_database IS 'Development Database'; COMMENT ON DOMAIN my_domain IS 'Email Address Domain'; COMMENT ON EVENT TRIGGER abort_ddl IS 'Aborts all DDL commands'; COMMENT ON EXTENSION hstore IS 'implements the hstore data type'; COMMENT ON FOREIGN DATA WRAPPER mywrapper IS 'my foreign data wrapper'; COMMENT ON FOREIGN TABLE my_foreign_table IS 'Employee Information in other database'; 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 MATERIALIZED VIEW my_matview IS 'Summary of order history'; COMMENT ON OPERATOR ^ (text, text) IS 'Performs intersection of two texts'; COMMENT ON OPERATOR - (NONE, integer) IS 'Unary minus'; COMMENT ON OPERATOR CLASS int4ops USING btree IS '4 byte integer operators for btrees'; COMMENT ON OPERATOR FAMILY integer_ops USING btree IS 'all integer operators for btrees'; COMMENT ON POLICY my_policy ON mytable IS 'Filter rows by users'; COMMENT ON PROCEDURE my_proc (integer, integer) IS 'Runs a report'; COMMENT ON PUBLICATION alltables IS 'Publishes all operations on all tables'; COMMENT ON ROLE my_role IS 'Administration group for finance tables'; COMMENT ON ROUTINE my_routine (integer, integer) IS 'Runs a routine (which is a function or procedure)'; 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 SERVER myserver IS 'my foreign server'; COMMENT ON STATISTICS my_statistics IS 'Improves planner row estimations'; COMMENT ON SUBSCRIPTION alltables IS 'Subscription for all operations on all tables'; COMMENT ON TABLE my_schema.my_table IS 'Employee Information'; COMMENT ON TABLESPACE my_tablespace IS 'Tablespace for indexes'; COMMENT ON TEXT SEARCH CONFIGURATION my_config IS 'Special word filtering'; COMMENT ON TEXT SEARCH DICTIONARY swedish IS 'Snowball stemmer for Swedish language'; COMMENT ON TEXT SEARCH PARSER my_parser IS 'Splits text into words'; COMMENT ON TEXT SEARCH TEMPLATE snowball IS 'Snowball stemmer'; COMMENT ON TRANSFORM FOR hstore LANGUAGE plpython3u IS 'Transform between hstore and Python dict'; 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';
SQL 標準中沒有 COMMENT 命令。
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