Retrieves a previously placed comment on a database object or definition.
For information about the comment-placing form of this SQL statement, see Teradata Vantage™ - SQL Data Definition Language Detailed Topics, B035-1184.
ANSI Compliance
COMMENT is a Teradata extension to the ANSI SQL:2011 standard.
Required Privileges
None.
Privileges Granted Automatically
None.
Rules for Using COMMENT (Comment-Retrieving Form)
These rules apply to using the comment-retrieving form of the COMMENT statement:
- COMMENT (Comment-Retrieving Form) is treated as a DML statement for transaction processing, so it can be used in 2PC session mode. For a brief description of the two-phase commit protocol, see Teradata Vantage™ - Database Introduction, B035-1091.
You can specify a COMMENT (Comment-Retrieving Form) request at any point within the boundaries of an explicit transaction in Teradata session mode.
- To retrieve a comment, do not specify a comment string following the specification of the object name.
IF you … THEN the system … specify a comment string does one of the following things: - If the specified object has no existing comment, the database places the specified comment string for the object in the data dictionary.
- If the specified object has an existing comment, the database replaces the existing comment in the data dictionary with the newly specified string.
do not specify a comment string does one of the following things: - If the specified object has no existing comment, the database returns a null.
- If the specified object has an existing comment, the database returns the text of that comment as it is stored in the data dictionary.
- You cannot specify a containing database or user name if the object kind you specify is GROUP.