如何在MongoDB中计算字符串总和？
要在MongoDB中计算字符串的总和，请使用aggregate()。让我们创建一个包含文档的集合-
> db.demo71.insertOne({"Price":"20"});
{
"acknowledged" : true,
"insertedId" : ObjectId("5e29af210912fae76b13d76e")
}
> db.demo71.insertOne({"Price":"50"});
{
"acknowledged" : true,
"insertedId" : ObjectId("5e29af240912fae76b13d76f")
}
> db.demo71.insertOne({"Price":"20"});
{
"acknowledged" : true,
"insertedId" : ObjectId("5e29af270912fae76b13d770")
}
> db.demo71.insertOne({"Price":"10"});
{
"acknowledged" : true,
"insertedId" : ObjectId("5e29af2d0912fae76b13d771")
}在find()方法的帮助下显示集合中的所有文档-
> db.demo71.find();
这将产生以下输出-
{ "_id" : ObjectId("5e29af210912fae76b13d76e"), "Price" : "20" }
{ "_id" : ObjectId("5e29af240912fae76b13d76f"), "Price" : "50" }
{ "_id" : ObjectId("5e29af270912fae76b13d770"), "Price" : "20" }
{ "_id" : ObjectId("5e29af2d0912fae76b13d771"), "Price" : "10" }以下是计算MongoDB中字符串总和的查询-
> db.demo71.aggregate([
... {
... $group: {
... _id: null,
... TotalPrice: {
... $sum: {
... $toInt: "$Price"
... }
... }
... }
... }
... ]);这将产生以下输出-
{ "_id" : null, "TotalPrice" : 100 }