TRUNC( ( to_char( SYSDATE, 'yyyyMMdd' ) - to_char( BIRTH_DATE, 'yyyyMMdd' ) ) / 10000 ) AS age

The above SQL code calculates the age of a person based on their birth date and the current date.

Explanation of the code:

- SYSDATE is a built-in function in Oracle that returns the current system date and time.
- to_char() is a function that converts a date or timestamp value to a character string in a specified format.
- 'yyyyMMdd' is the date format used in this code, where 'yyyy' represents the year with four digits, 'MM' represents the month with two digits, and 'dd' represents the day with two digits.
- BIRTH_DATE is a column name in a table that stores the birth date of a person.
- The subtraction of the birth date from the current date yields the number of days between the two dates. This value is divided by 10000 to convert the number of days to years.
- TRUNC() is a function that truncates a number to a specified number of decimal places. In this code, it is used to remove any fractional part from the age value.

Overall, the code calculates the age of a person by subtracting their birth date from the current date, converting the result from days to years, and truncating any fractional part.