我似乎找不到解决这个问题的办法.我就是不知道怎么了.
我已经试过Mongo subtract in group aggregation次了,但没有希望.邮报也没有进一步解释.
这是我的代码:
var aggregateOptions;
aggregateOptions = [{
$match: {
}
},{
$group: {
_id: "$customerID",
totalAmount: { $sum: "$amount" },
totalpaidAmount: { $sum: "$paidAmount" },
totalAmountDue: { $subtract: ["$totalAmount", "totalpaidAmount"] }
}
}];
Sale.sales.get(Sale.Schema, aggregateOptions, (err, saleRecord) => {
if (err) throw err;
console.log(saleRecord);
res.json({
pageTitle: "Customer List",
currentUser: req.user,
saleRecord: saleRecord,
});
});
它会提示MongoError:$subtract累加器在每次查询时都是一元运算符.