text: A comment is an arbitrary sequence of characters beginning with two consecutive hyphen characters and extending to the end of the line. For example:
  -- This is a standard SQL comment
  A comment is removed from the input stream before further syntax analysis and is effectively replaced by white space.
  Alternatively, C-style block comments can be used where the comment begins with /*
  and extends to the matching occurrence of */
  /* multiline comment
  * with nesting: /* nested block comment */
  These block comments nest, as specified in the SQL standard. Unlike C, you can comment out larger blocks of code that might contain existing block comments.