How to read a database scheme?

Hi,
I wanted to ask if anyone could explain to me how to read a database scheme that looks like the one on the picture?
The relations drawn by lines within the tables I do partially understand - if there’s a fork it means that the entity can have 1 or more of the other entity (for example HR departments can only have one HR location however locations can have several HR departments). But I do not understand why are they not connected with a full line?
I also do not understand what does the arrow coming from HR employees pointing back the HR employees mean?

Thank you for any help

I’m not sure b/c I’m not familiar w/Oracle SQl server. I would assume it’s PRIMARY and FOREIGN KEY ?

@coffeencake is the expert on Oracle…perhaps she can offer some insights? :slight_smile:

2 Likes

Hello!

Yes @lisalisaj that is correct, p is for PRIMARY key, f for FOREIGN key and u for UNIQUE key.

Yes @kira7271370673 that is also correct. The fork means or “crows feet” that there is a 1 to Many relationship between HR.Locations and HR Departments. The full lines show a mandatory relationship between the tables. The dotted lines are an optional relationship.

Sometimes it helps to look at the data in the table too.

I hope that helps. Let me know if you have any more questions.

3 Likes