When to use Associative entities?
<p>Suppose there are two entities called Employee and Campaign. One employee can work on many campaigns. And one campaign can have many employees. I already know this is a many to many relationship.</p>

<p>And when drawing the ER diagram (in Chen notation), the relationship is symbolized by a diamond shape. But there is a separate symbol for associative entities, which symbolizes a many to many relationship between two entities.</p>

<p>1) So should I use the diamond shape or the associative entity shape (diamond inside a square) when drawing many to many relationships in er diagram in Chen's notation?<br>
2) Do they both mean the same thing or different things?<br>
3) If they are two separate things, how can I identify when to use which?</p>