numtoyminterval converts number n to an INTERVAL YEAR TO MONTH literal. n can be a number or an expression resolving to a number. char_expr can be of CHAR, VARCHAR2, NCHAR, or NVARCHAR2 datatype. The value for char_expr specifies the unit of n, and must resolve to one of the following string values:
char_expr is case insensitive. Leading and trailing values within the parentheses are ignored. By default, precision of the return is 9.