query:      `SELECT date_diff(year, '2010-01-01T', '2011-01-01T') FROM S3Object LIMIT 1`,
			wantResult: `{"_1":1}`,
		},
		{
			name:       "date_diff_year",
			query:      `SELECT date_diff(month, '2010-01-01T', '2010-05T') FROM S3Object LIMIT 1`,
			wantResult: `{"_1":4}`,
		},
		{
			name:       "date_diff_month_oney",
			query:      `SELECT date_diff(month, '2010T', '2011T') FROM S3Object LIMIT 1`,

	sqlFnCoalesce FuncName = "COALESCE"
	sqlFnNullIf   FuncName = "NULLIF"

	// Conversion
	sqlFnCast FuncName = "CAST"

	// Date and time
	sqlFnDateAdd     FuncName = "DATE_ADD"
	sqlFnDateDiff    FuncName = "DATE_DIFF"
	sqlFnExtract     FuncName = "EXTRACT"
	sqlFnToString    FuncName = "TO_STRING"
	sqlFnToTimestamp FuncName = "TO_TIMESTAMP"
	sqlFnUTCNow      FuncName = "UTCNOW"

	// String

}

// dateDiff computes the difference between two times in terms of the
// `timePart` which can be years, months, days, hours, minutes or
// seconds. For difference in years, months or days, the time part,
// including timezone is ignored.
func dateDiff(timePart string, ts1, ts2 time.Time) (*Value, error) {
	if ts2.Before(ts1) {
		v, err := dateDiff(timePart, ts2, ts1)
		if err == nil {

	case sqlFnDateAdd:
		result.combine(e.DateAdd.Quantity.analyze(s))
		result.combine(e.DateAdd.Timestamp.analyze(s))
		return result

	case sqlFnDateDiff:
		result.combine(e.DateDiff.Timestamp1.analyze(s))
		result.combine(e.DateDiff.Timestamp2.analyze(s))
		return result

	// Handle aggregation function calls
	case aggFnAvg, aggFnMax, aggFnMin, aggFnSum, aggFnCount:
		// Initialize accumulator