Adds a specified number of days to a date.
The required date must evaluate to a datetime. The required number-of-days must be an integer.
This is a convertible function resolved by USoft and thus supported on all RDBMS platforms.
On Oracle and SQL Server, in additions and subtractions involving a date value and a numeric value, the numeric value is automatically converted to a date value (1 is interpreted as 1 day). On JDBC/Derby, ADD_DAYS must be used to achieve this conversion.