What symbols are used in SQL to indicate a comment that should not be executed in a query?

In SQL, a double dash (--) is used to indicate that everything following it on that line is a comment and should not be executed as part of the query. This allows developers to include notes or explanations within their SQL code without affecting the functionality of the actual queries. Anything on the same line after the double dash will be ignored by the SQL interpreter, which is useful for documenting code or temporarily disabling parts of a query.

The other options provided are also related to comments in SQL but apply different contexts. For instance, using /* and */ denotes a multi-line comment, which allows for longer comments spanning multiple lines. Choosing double dashes, on the other hand, is specific to single-line comments. Thus, while multiple comment styles exist in SQL, the double dash is particularly used for comments that are confined to a single line.