4.6.2 Intervals

There are two classes of intervals. One class, called year-month intervals, has an express or implied datetime precision that includes no fields other than YEAR and MONTH , though not both are required. The other class, called day-time intervals, has an express or implied interval precision that can include any fields other than YEAR or MONTH .

The actual subset of fields that comprise a value of either type of interval is defined by an <interval qualifier> and this subset is known as the precision of the value. Within a value of type interval, the first field is constrained only by the <interval leading field precision> of the associated <interval qualifier> . Table 6, Valid values for fields in INTERVAL values, specifies the constraints on subsequent field values.

