フリー問題

問題文

A query has to call a function of the schema inside its select list. Which description of the conditions that such a function has to meet is correct?

選択肢

1. Its parameters have to be declared in the mode that returns a value to the caller, and the value that it returns has to be of a type that only PL/SQL knows, so a boolean result is the usual choice for such a function.
2. Its name has to differ from the name of every column in the query, and the value that it returns has to be a character string, so a numeric result has to be converted before the call.
3. Its body has to be written without any declarative part, and the value that it returns has to be computed from the parameters alone, so a function that reads a table cannot be named in a select list.
4. Its parameters have to be of the modes and the types that a SQL statement can supply, and the value that it returns has to be of a type that a SQL statement is able to use in the same way.