relation

How i can override manager for relations? For example: user.entry_set # django.db.models.fields.related.RelatedManager But i need for my own manager. I try this code, but this does not work: class EntryManager(models.Manager): use_for_related_fields = True Thanks. You task requires rather hacky code which will be very hard to maintain and understand (if it's even possible). What about this? class EntryManager(models.Manager): def by_user(self, user): # do anything you want # usage Entry.objects.by_user(user=user) 来源： https://stackoverflow.com/questions/10547583/override-djangos-relatedmanager

I need some help and guidelines. I have the following relation: R = {A, B, C, D, E, F} and the set of functional dependencies F = { {AB -> C}; {A -> D}; {D -> AE}; {E -> F}; } What is the primary key for R ? If i apply inference rules i get these additional Function dependencies: D -> A D -> E D -> F D -> AEF A -> E A -> F A -> DEF How do I continue? There is a well known algorithm to do this. I don't remember it, but the excercise seems to be simple enough not to use it. I think this is all about transitivity: CurrentKey = {A, B, C, D, E, F} You know D determines E and E determines F. Hence,

I am recently working on using nltk to extract relation from text. so i build a sample text:" Tom is the cofounder of Microsoft." and using following program to test and return nothing. I cannot figure out why. I'm using NLTK version: 3.2.1, python version: 3.5.2. Here is my code: import re import nltk from nltk.sem.relextract import extract_rels, rtuple from nltk.tokenize import sent_tokenize, word_tokenize def test(): with open('sample.txt', 'r') as f: sample = f.read() # "Tom is the cofounder of Microsoft" sentences = sent_tokenize(sample) tokenized_sentences = [word_tokenize(sentence) for

I can't get the onDelete to work in Doctrine2 (with YAML Mapping). I tried this relation in my Product class: oneToOne: category: targetEntity: Category onDelete: CASCADE But that doesn't work.. EDIT: I've set the ON DELETE: CASCADE manually in the database imported the YAML mapping with doctrine:mapping:import , emptied the database updated it from the schema with doctrine:schema:update and got no ON DELETE in the foreign key.. so looks like even Doctrine doesn't know how to do it lol.. OK, got it! I had to use onDelete inside joinColumn : oneToOne: category: targetEntity: Category joinColumn

This seems like an easy query but I cannot seem to get it or relate it to other posts on stack overflow. Would anyone be able to explain... This is what I have so far, it is returning records for all bars where one or both people go. TBL frequents Schema - drinker VARCHAR(50) PK, bar VARCHAR(50) PK Bars which are frequented by John or Rebecca but not by both of them SELECT DISTINCT bar FROM frequents WHERE drinker = 'John' XOR drinker = 'Rebecca' AND bar NOT IN ( SELECT f1.bar FROM frequents f1, frequents f2 WHERE ( f1.drinker = 'John' AND f2.drinker = 'Rebecca' AND f1.bar = f2.bar ) );

Need to find all words with their Italian translation, if Italian doesn't exist, then need with Spanish (default language). I can`t use more than one query, and where exists condition(technical limitations) Words id|name ------- 1|Dog 2|Cat Translations id|word_id|translation|language ------------------------------- 1| 1| Perro|es 2| 1| Cane |it 3| 2| Gatto|es Result: id|name|translation|language 1| Dog| Cane|it 2| Cat| Gatto|es SELECT * FROM words LEFT JOIN translation ON words.id = translation.word_id WHERE language = 'it' OR (language = 'es' AND NOT EXISTS(SELECT * FROM translation WHERE