when using MySQL, such as connecting to MySQL, with Django, a new field is added to model. As long as you do migration, on the command line, this field will be added to all previous records, but how to do it in MongoDB? Nodejs as a backend, does it have this function?
does it mean to open MongoDB directly and then command line update? Is there a migration tool like Django?
MongoDB is a non-relational database, and there is no concept of columns. It means you don't have to add a new blank column to every document, yes or no, and it doesn't affect your use.
when deploying, execute the mongo command and add the field command: db.yourtable.update ({}, {$set: {addField: ""}}, false,true)
Next: Css class name problem
Project.updateOne(r, { $pull: { thunder2: { files: { _id: "5ab362d446f15936bcea7dd3" } } } }, function(err, data) { if (err) { res.send("") } else { ...
the previous command is as follows: mongod --logpath C: mydatabase logs.txt --logappend --dbpath C: mydatabase --serviceName MongoDB --install however, there is no prompt on the command line after entering the carriage enter, and the service has ...
the query data is printed to see that _ id is objectID,. If it is directly converted to json,_id, it will be empty. Can you change objectID to string, and then to json? ...
Virtual properties are document properties that you can get and set but that do not get persisted to MongoDB. I don t quite understand this sentence. Please do not translate. I hope you can explain it in your own words. It is better to have examples. ...
first of all, according to the description of the official document, the configuration file is created and the database path is modified. The content of the configuration file mongo.config is as follows: systemLog: destination: file path: I: ...
suddenly became interested in mongodb, installed and started with brew according to the rookie tutorial, but showed "waiting for connections on port 27017 " for a long time, then as a front-end younger brother who still has a narrow range of knowle...
Mode 1: mongod Command Mode 2: brew services start mongodb Command start what s the difference between the two ways of starting? why are there two ways? ...
the company recently has a project, the main function is to manage documents, such as on the web page to view the contents of the document, and can be modified, you can also download the document to export in word format, the most important thing is to r...
assume a single document type: { "_id" : ObjectId("5a19403b421aa92332bc2b32"), "id" : "95957f4a9eab11e787f1509a4c4be0cd" "incre" :1 "city" "" } data volume, 90 mill...
var animalSchema = new Schema({ name: String, type: String }); animalSchema.methods.findSimilarTypes = function(cb) { return this.model( Animal ).find({ type: this.type }, cb); }; var Animal = mongoose.model( Animal , animalSchema); var dog = new A...
the computer is a WIN 10 system I follow this tutorial to install mongoDB, http: www.runoob.com mongodb. but as soon as you enter the mongo link. Just report this error has been reinstalled several times, but it has not been solved. also chan...
ip and port are OK on the server! bind_ip 0.0.0.0 ip ask the boss to have a look. No, no, no. It s okay to pay for an answer! ...
data stores a field type (as an enumeration). When querying, it needs to be processed separately by using ifelse or switch, for example, 1 is converted to normal. I ve implemented it with the MongoDB statement, but how do I handle it in the springboot ...
there is data like this: I want to use aggregate to group group by p, and then count the sum of ac, cc in each province, which can be done. The question is: I want to count the total number of tc in each province (do not repeat)? For example, Fujia...
I tried to do this, but could not copy set initialization. ...
the problem is like a question. I ll describe the details in detail. asked the same question on Zhihu when I was self-taught python crawler, I came into contact with MongoDB, to install according to the URL given by rookie tutorial . Visual obser...
first of all, the models of my mongoose is as follows: var clubsSchema = new mongoose.Schema({ "clubCreatetime": String, "clubCreater": String, "clubName": String, "clubDescription": String, &...
there are 200000 data in the data, and each data has a typical list of words of 5000 length [{aVl1}, {bju 2},.], and typical dictionaries of 5000 length {{aRom 1}, {bjr 2},.}, use pyMongo to find100 data, the traversal of cursor is particularly slow, is...
You can stream query results from MongoDB. You need to call the Query-sharpcursor () function to return an instance of QueryCursor. Please do not translate directly. I want to know what cursor is and what stream is, and why I use it, thank you! ...
mongodb doesn t seem to have the join functionality of sql. Reducing the redundancy of individual tables does not seem to make sense and affects query efficiency. and mongodb also has storage formats such as lists, which can achieve different function...