Which two statements are true about substitution variables?
A.A substitution variable used to prompt for a column name must be enclosed in double quotation正确答案DF
Marks. B.A substitution variable prefixed with s always prompts only once for a value in a session C.A substitution variable used to prompt for a column name must be enclosed in single quotation
Marks D.A substitution variable prefixed with && prompts only once for a value in a session unless it is
Set to undefined in the session E.A substitution variable can be used only in a SELECR statement F.A substitution variable can be used with any clause in a select statement
