Quantity  *Operand     `parser:" @@ \",\""`
	Timestamp *PrimaryTerm `parser:" @@ \")\""`
}

// DateDiffFunc represents the DATE_DIFF function
type DateDiffFunc struct {
	DatePart   string       `parser:" \"DATE_DIFF\" \"(\" @( \"YEAR\":Timeword | \"MONTH\":Timeword | \"DAY\":Timeword | \"HOUR\":Timeword | \"MINUTE\":Timeword | \"SECOND\":Timeword ) \",\" "`
	Timestamp1 *PrimaryTerm `parser:" @@ \",\" "`

	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