Meaning of "n:m" and "1:n" in database design

mysql database foreign-keys relationship
Abdullah Khan picture Abdullah Khan · Aug 3, 2010 · Viewed 165.5k times · Source

In database design what do n:m and 1:n mean?

Does it have anything to do with keys or relationships?

Answer

Matti Virkkunen picture Matti Virkkunen · Aug 3, 2010

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).

Related questions

Can table columns with a Foreign Key be NULL?

I have a table which has several ID columns to other tables. I want a foreign key to force integrity only if I put data in there. If I do an update at a later time to populate that column, …

Read More
Foreign key constraints: When to use ON UPDATE and ON DELETE

I'm designing my database schema using MySQL Workbench, which is pretty cool because you can do diagrams and it converts them :P Anyways, I've decided to use InnoDB because of it's Foreign Key support. One thing I noticed though is …

Read More
MySQL foreign key to allow NULL?

I'm piecing together an image website. The basic schema's pretty simple MySQL, but I'm having some trouble trying to represent possible admin flags associated with an image ("inappropriate", "copyrighted", etc.). My current notion is as follows: tblImages ( imageID INT UNSIGNED …

Read More