data-modeling

问题 I am building an app on google app engine which has three different kind of Users(ABC,LMN,XYZ). This is how my model looks like User(db.Model): email = db.EmailProperty() username = db.StringProperty() password = db.StringProperty() role = db.IntegerProperty() ## role = 1 for ABC;2 for LMN;3 for XYZ ABC(User): name = db.StringProperty() isSuperHero = db.BooleanProperty() LMN(User): nickname = db.StrngProperty() profession = db.StringProperty() # some other random property XYZ(User):

问题 I want to plot a graph over a year+weeknumber on the x axis. Each data-point contains this specific value; for example week 7 of 2016 is expressed as 201607 etc. and called YearWeek I created a date table in which I calculate all possible YearWeek value in a certain date-range. Then I created a YearWeek table extracting all distinct YearWeeks. This I connected to the Fact-Table. What I want to chart is exactly according to this matrix: Note that I explicitly selected to show items with no

问题 In normal 2 or multi class classification problem, we can use any famous machine learning algorithm like Naive Bayes or SVM to train and test the model. My problem is that I have been given weather data where the label variable is in the format of "20 % rain, 80 % dry" or "30% cloudy, 70% rain" etc. How should I approach this problem? Will I need to covert the problem into regression somehow? In that case, if there are three labels (rain, dry, cloudy) in data, what may be the right approach

问题 I have used google sheet function IMPORTXML for scraping specific parts of webpages but It's not working properly with long xpath, not fluent, not smooth on tons of websites URL. I have also tried distill extension, excel scraping from web table but It is also not long term smooth solution. Please help to get notified on changes / updation of specific parts of tons of webpages. 来源： https://stackoverflow.com/questions/54444976/get-many-webpages-updation-alerts-systematic-automated-web-scraping

问题 I'm trying to mimic something like this: Given a table test : CREATE TABLE myspace.test ( item_id text, sub_id text, quantity bigint, status text, PRIMARY KEY (item_id, sub_id) In SQL, we could do: select * from (select item_id, sum(quantity) as quan from test where status <> 'somevalue') sub where sub.quan >= 10; i.e. group by item_id and then filter out the results with less than 10. Cassandra is not designed for this kind of stuff though I could mimic group by using user-defined aggregate

问题 coming from angular i used to have a class for every entity in my DB, such class encapsulated all entity behaviour. for example users Class can look like export class User{ static notValid(u){ return !!((u.id && u.id > 0 && u.fullname && u.fullname.length > 2 && u.picture) === false); } static fromArray(arr){ let pack = []; for(let i=0;i<arr.length;i++){ pack.push(new User(arr[i])); } return pack; } constructor(u){ this.id = u.id || 0; this.fullname = u.fullname+'' || 'N/A'; this.picture = u

问题 Closed. This question is off-topic. It is not currently accepting answers. Want to improve this question? Update the question so it's on-topic for Stack Overflow. Closed last year . At some point, I assume that anyone developing for couchdb (or other nosql option) must still identify what must be stored in each document. And it would seem that, although very rarely, every once in a while we would need to have some relationships between these documents. So, are people still using ER-type

问题 How do I convert "YANG" data model to "JSON"? As there is many many docs available in web, in that they changed in YANG synatx to JSON but how the value for the leaf or leaf list they are getting? from where and how it will get actual data in JSON from YANG? 回答1: Convert yang to xml using pyang -f yin filename Convert xml file to json using any of the solutions below https://stackoverflow.com/a/10201397/3283069 https://stackoverflow.com/a/6465496/3283069 回答2: Yang is a modeling language, not

问题 I have recently moved to MongoDB part of the back-end of a web app, the web app itself is a validation tool, and the workflow looks like: the user uploads a file (typically hundreds of thousands of lines) the validator checks it outputting a lot of messages (possibly more than one per line) ...and finally provide a few statistics I modelled my application so that each user has it's own DB containing: The file (saved through GridFS) A collection containing the messages (possibly over a million

问题 When two tables have a many-to-many relationship or when a table has a many-to-many relationship with itself we can model that with a junction table. However the type of the relationship can expend beyond the original type, for example: Requirements: we have users. each user can have 0 or more other users as friends Solution: a users table and a junction table called "user_user". Then we discover a new requirement: some friendships are romantic or in other words two users can be connected in