Syntax:
TIMESTAMPADD(interval,int_expr,datetime_expr)

Adds the integer expression int_expr to the date or datetime expression
datetime_expr. The unit for int_expr is given by the interval argument,
which should be one of the following values: FRAC_SECOND, SECOND,
MINUTE, HOUR, DAY, WEEK, MONTH, QUARTER, or YEAR.

The interval value may be specified using one of keywords as shown, or
with a prefix of SQL_TSI_. For example, DAY and SQL_TSI_DAY both are
legal.
