foreign-keys

问题 I have a table called 'agenda' //translation: dairy with the following rows: idagenda // primary key title waar organisatie ... etc. ... I also have a table for the date of an diary item/event called agendadatum with the following rows: id // primary key idagenda // id from other table van //from tot // till datum // date When the field 'tot' is the date from Today it will delete the rows from the database, but the rows in the 'agenda' table remain untouched. They're not deleted, because I

问题 I have a Database With a foreign key I am using the SELECT * FROM statement but I keep getting an error when I try to view the database. SELECT * FROM STATEMENT private final String MY_QUERY = "SELECT * FROM wwTable mLat INNER JOIN wwTimeTable _id ON wwTable._id=wwTimeTable.mName WHERE Table._id=wwTimetabel.mForeign"; MY KEYS public static final String KEY_ROWID = "_id"; public static final String KEY_ROWIDLL = "_id"; public static final String KEY_ROWIDTIME = "_id"; public static final

问题 i'm building a DB of a graduation projects management system. Students are divided into groups .There is groups table and faculty table. Each group has an advisor and two examiners. i'm confused here. Should i create 3 FKs from the the faculty table? 2 for examiners and 1 for advisor? here is the SQL code: create table groups ( groupID NUMBER not null, nbStudents NUMBER not null, avgGPA DOUBLE NOT NULL, projectName varchar(50) not null, advisorID NUMBER examiner1ID NUMBER examiner2ID NUMBER

问题 This is for a sort of proof of concept draft to get things working, but don't want to have completely crap code. For my database, I tried to get true foreign key relations going using innoDB, but couldn't get it. Instead of using foreign keys, I decided to just pull mysql_insert_id() after inserts, saving it as a variable, then putting that variable into the related table. Is this horrible? Everything seems to work well, and I'm able to connect and relate ID's as needed. What benefits would

问题 I have an app with a similar structure as this snippet class Blog(models.Model): name = models.CharField(max_length=25) class Category(models.Model): name = models.CharField(max_length=25) blog = models.ForeignKey(Blog) class Entry(models.Model): title = models.CharField(max_length=25) category = models.ForeignKey(Category) What is the most generic way, that i will be able to use in other apps to fetch all blogs with their category and entries? I thought about creating a manager for the Blog

问题 had an issue before with this code which was resolved and caused the table to work but now i am receiving error 1005 and the table cannot be created due to the fk here is the code for the first table SET FOREIGN_KEY_CHECKS = 0; DROP TABLE IF EXISTS Customer; CREATE TABLE Customer ( CustomerNumber int NOT NULL, CustomerName varchar(255), CustomerAddress varchar(255), CustomerPhoneNumber varchar(255), JoinDate varchar(255), PetName varchar(255), PayScheme varchar(255), PremiumPayDate varchar

问题 I am starting to experiment with using InnoDB in web applications. I've setup some tables with a foreign key, but they are not behaving as expected. Here are my table CREATE statements: CREATE TABLE sections ( section_id INT NOT NULL AUTO_INCREMENT, title VARCHAR(30), created_at int(10) NOT NULL, updated_at int(10) NOT NULL, PRIMARY KEY(section_id) ) ENGINE=InnoDB; CREATE TABLE pages ( page_id INT NOT NULL AUTO_INCREMENT, section_idfk INT NOT NULL, PRIMARY KEY(page_id), FOREIGN KEY(section

问题 I have absolutely no clue why MySQL is having an issue with the second CREATE TABLE statement. CREATE TABLE User( uid INTEGER, url CHAR(100), firstname CHAR(40), lastname CHAR(40), PRIMARY KEY(uid) ); The below is the one that causes problems: CREATE TABLE Follows( uid INTEGER, url CHAR(100), PRIMARY KEY(uid,url), FOREIGN KEY(uid) REFERENCES User(uid), ON DELETE CASCADE, FOREIGN KEY(url) REFERENCES User(url), ON DELETE CASCADE ); Error I get is: #1064 - You have an error in your SQL syntax;

问题 what i need is to allow users to access list of Parent objects by filtering their related objects `Kid' We have a dictionary that has a 100 kid. and parents that have about 5 kids in average. if the kids in 1 parent object are all in the dictionary I want them to be listed. But not all 100 kid have to be related to the parent object. e.g if the parent have 4 kids who are in the dictionary and 1 that is not. Then do not include them. I have the code below models.py : class Parent(models.Model)

问题 In SQL Server 2012, can I create a foreign key constraint that includes a restriction on which rows can be referenced based on other keys? Example: CREATE TABLE Client ( Id INT IDENTITY PRIMARY KEY Description NVARCHAR(200) ); CREATE TABLE Location ( Id INT IDENTITY PRIMARY KEY, Description NVARCHAR(200), ClientId INT NOT NULL, FOREIGN KEY (ClientId) REFERENCES Client(Id) ); CREATE TABLE Defect ( Id INT IDENTITY PRIMARY KEY, Description NVARCHAR(200), ClientId INT NOT NULL, LocationId INT