switch e.getFunctionName() {
	case sqlFnCast:
		expr := e.Cast.Expr
		res, err = expr.castTo(r, strings.ToUpper(e.Cast.CastType), tableAlias)
		return

	case sqlFnSubstring:
		return handleSQLSubstring(r, e.Substring, tableAlias)

	case sqlFnExtract:
		return handleSQLExtract(r, e.Extract, tableAlias)

	case sqlFnTrim:
		return handleSQLTrim(r, e.Trim, tableAlias)

	case sqlFnDateAdd: