The language supports comments in both DML and DDL statements. Such comments have the same semantics as comments in a regular programming language, that is, they are not stored anywhere, and have no effect to the execution of the statements. The following comment constructs are recognized:
/* comment */

Potentially multi line comment.


However, if a '+' character appears immediately after the opening "/*", and the comment is next to a SELECT keyword, the comment is actually not a comment but a hint for the query processor. See Choosing the Best Applicable Index.
// comment

Single line comment.

# comment

Single line comment.

As we will see, DDL statements may also contain comment clauses, which are stored persistently as properties of the created data entities. Comment clauses start with the COMMENT keyword, followed by a string literal, which is the content of the comment.


comment ::= COMMENT string