foreign-keys

In database design what do n:m and 1:n mean? Does it have anything to do with keys or relationships? m:n is used to denote a many-to-many relationship ( m objects on the other side related to n on the other) while 1:n refers to a one-to-many relationship ( 1 object on the other side related to n on the other). 1:n means 'one-to-many'; you have two tables, and each row of table A may be referenced by any number of rows in table B, but each row in table B can only reference one row in table A (or none at all). n:m (or n:n) means 'many-to-many'; each row in table A can reference many rows in

Similar to this question but for MySQL.... How can I programmatically determine foreign key references in MySQL (assuming InnoDB)? I can almost get them with: SHOW TABLE STATUS WHERE Name = 'MyTableName'; ...but alas, the comment column which seems to contain some of this info gets truncated so I can't rely on it. There must be some other way... I'd be happy with a C API call, a SQL statement, anything--I just need something that consistently works. Note: I've also considered parsing the results of a "SHOW CREATE TABLE MyTableName" statement, but I'm really hoping there's something simpler.

I have several Customer s who book Appointment s. Each Appointment has exactly one customer, though a customer can be booked for multiple appointments occurring at different times. class Customer(model.Model): def __unicode__(self): return u'%s' % (self.name,) name = models.CharField(max_length=30) # and about ten other fields I'd like to see from the admin view. class Appointment(models.Model): datetime = models.DateTimeField() customer = models.ForeignKey("Customer") class Meta: ordering = ('datetime',) Now when an admin goes to browse through the schedule by looking at the Appointments

I wanted a Django model with 2 foreign keys from the same table. It's an event table which has 2 columns for employees: the 'actor' and the 'receiver'. But I get this error: Error: One or more models did not validate: tasks.task: Intermediary model TaskEvent has more than one foreign key to Employee, which is ambiguous and is not permitted. Is there a better way to model this? Thanks I think I'm going to add a TaskEvent_to_Employee table. There will be two records in it, one for each of the two employees related to each TaskEvent . Anyone know an easier workaround? I haven't done this yet, but

We have some models that are have a user as a foreign key. But with about 25000 users in our system, it's a bit daunting to find the one we need. Is there a solution out there that's better than the select box? Maybe an autocomplete so we can start typing the user name / address? Or just a search box? When switching the related user for these objects, it's getting harder and harder with 25000 unsorted users. Even just setting it to sort the users by username would be helpful. Etienne I had this problem and my conclusion was to use an autocomplete field instead. It works pretty well in most

I've been trying to get foreign keys working within my Android SQLite database. I have tried the following syntax but it gives me a force close: private static final String TASK_TABLE_CREATE = "create table " + TASK_TABLE + " (" + TASK_ID + " integer primary key autoincrement, " + TASK_TITLE + " text not null, " + TASK_NOTES + " text not null, " + TASK_DATE_TIME + " text not null, FOREIGN KEY ("+TASK_CAT+") REFERENCES "+CAT_TABLE+" ("+CAT_ID+"));"; Any ideas what I might be doing wrong? if you need to see the other table structure then I can, its just a very simple structure for the second