## COMMENT ON Statement (comment_on_statement)

The COMMENT ON statement (comment_on_statement) alters or drops a comment for a database object stored in the database catalog.

### Syntax

<comment_on_statement> ::= COMMENT ON <object_spec> IS <comment>

<object_spec> ::= see explanation
<comment> ::= <string_literal> | <parameter_name>

### Explanation

Comments can be specified for the following database objects:

<object_spec> ::= | Explanation
COLUMN <table_name>.<column_name> | The column must exist in the specified table. The current user must be the owner of the table. The comment for this column can be requested by selecting the system table DOMAIN.COLUMNS.
DBPROC[EDURE] <dbproc_name> | dbproc_name must identify an existing database procedure, the owner of which is the current user. A comment is stored for the DB procedure. The comment can be requested by selecting the system table DOMAIN.DBPROCEDURES.
DOMAIN <domain_name> | domain_name must specify a domain for the current user. The comment for this domain can be requested by selecting the system table DOMAIN.DOMAINS.
FOREIGN KEY <table_name>.<referential_constraint_name> | referential_constraint_name must specify a referential CONSTRAINT definition for the specified table. The current user must be the owner of the table. The comment for this referential CONSTRAINT definition can be requested by selecting the system table DOMAIN.FOREIGNKEYS.
INDEX <index_name> ON <table_name> | index_name must specify an index of the specified table. The current user must be the owner of the table. The comment for this index can be requested by selecting the system table DOMAIN.INDEXES.
SEQUENCE <sequence_name> | An existing sequence must be specified using sequence_name. The current user must be the owner of the sequence. The comment for this sequence can be requested by selecting the system table DOMAIN.SEQUENCES.
[PUBLIC] SYNONYM <synonym_name> | synonym_name must specify a synonym of the current user. If PUBLIC is specified, the synonym must have the PUBLIC attribute. The comment for this synonym can be requested by selecting the system table DOMAIN.SYNONYMS.
TABLE <table_name> | The specified table must identify a base or view table of the current user that is not a temporary table. The current user must be the owner of the table. The comment for this table can be requested by selecting the system table DOMAIN.TABLES.
TRIGGER <table_name>.<trigger_name> | The specified trigger name must identify a trigger of the specified table. The current user must be the owner of the table. A comment is stored for the trigger and can be requested by selecting the system table DOMAIN.TRIGGERS.
USER <user_name> | The specified user must identify an existing user whose owner is the current user. The comment for this user can be requested by selecting the system table DOMAIN.USERS.
USERGROUP <usergroup_name> | The specified user group must identify an existing user group whose owner is the current user. The comment for this usergroup can be requested by selecting the system table DOMAIN.USERS.
<parameter_name> | The corresponding variable must contain one of the values listed in the table. The values must be encapsulated in inverted commas. Example: 'COLUMN <table_name>.<column_name>'