I’m designing a simple registration system for a website, that lets users register only if they are accepted by certain criteria (radio buttons selected) . My entities are:

Potential customers, Po_cus PK
----------------------------------------
User name, User_id PK
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Password, Pass_id PK
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User name, password (Composite table)
User_Id FK
Pass_Id FK
------------------------------------------------
Eligible, Pass_Id

I have created an erd however I seem to have created a loop between password, username and potential customer. Oh btw ive separated username and password for security reasons. Any ideas on how to break the loop would be handy thanks.

i don't see any connection from potential customer to any other entity at all

Sorry forgot to add,

Potential customers, Po_cus PK
----------------------------------------
User name, User_id PK
Po_cus FK
---------------------------------------
Password, Pass_id PK
----------------------------------------
User name, password (Composite table)
User_Id FK
Pass_Id FK
------------------------------------------------
Eligible, Passed_Id PK
Po_cus FK

I tend to focus more on the html side, bit new at the DB bit.

just curious, why did you decide to build an ERD?

and what's the logical difference between your Eligible entity and your Composite entity? they have exactly the same columns

Altered, your right made no sense. As for the reasons i thought it might make things clearer in my head , when it came to coding the application and to make the sql quires alittle easier, i hope.

Hi Just to let you know ive sorted the loop problem, if there is anything any of you would like to add or comment on feel free.

separating the username and password, and then tying them together again in a relationship table... seems like a lot of extra effort for no benefit whatsoever

How about then just using a foreign key to connect them? i was doing it for security but what would you suggest. ?

how about putting the password right in the user table