input: [Name] dtd_identifier [Description] An identifier of the data type descriptor of the return data type of this function, unique among the data type descriptors pertaining to the function. This is mainly useful for joining with other instances of such identifiers. (The specific format of the identifier is not defined and not guaranteed to remain the same in future versions.) [Data Type] 
output: sql_identifier
options: s q l _ i d e n t i f i e r
options: c h a r a c t e r _ d a t a
options: c a r d i n a l _ n u m b e r
options: y e s _ o r _ n o
options: t i m e _ s t a m p