A date and time interval is special value to be used to increment or decrement a date or a time at a given date or time unit. A data and time interval should be expression in the format of "INTERVAL expression unit", where "unit" and "expression" should follow these rules:

unit    expression value format

MICROSECOND  MICROSECONDS 

SECOND   SECONDS 

MINUTE   MINUTES 

HOUR    HOURS 

DAY   DAYS 

WEEK    WEEKS 

MONTH   MONTHS 

QUARTER   QUARTERS 

YEAR    YEARS 

SECOND_MICROSECOND 'SECONDS.MICROSECONDS' 

MINUTE_MICROSECOND 'MINUTES.MICROSECONDS' 

MINUTE_SECOND  'MINUTES:SECONDS' 

HOUR_MICROSECOND  'HOURS.MICROSECONDS' 

HOUR_SECOND  'HOURS:MINUTES:SECONDS' 

HOUR_MINUTE  'HOURS:MINUTES' 

DAY_MICROSECOND 'DAYS.MICROSECONDS' 

DAY_SECOND   'DAYS HOURS:MINUTES:SECONDS' 

DAY_MINUTE   'DAYS HOURS:MINUTES' 

DAY_HOUR   'DAYS HOURS' 

YEAR_MONTH   'YEARS-MONTHS'