Easy as 1,2,3 -- plus 4 & 5 can be.
Duke Ganote, July 03, 2012 - 5:29 pm UTC
IMHO, one can't beat Bill Kent's exposition of the normal forms. http://www.bkent.net/Doc/simple5.htm
According to Bill [Kent], the 3NF mantra is "a non-key field must provide a fact about the key, the whole key, and nothing but the key"
4th & 5th normal forms aren't intimidating. I think of them as basically "don't cheat by putting every field into the key".
I think of EAV data models as a variant of that kind of cheating.
Am not sure, but I think the emp table is not in 3NF
AJ, November 25, 2020 - 11:55 am UTC
As far as I understand, the emp table is not in 3NF as (Deptno, Job) determine the Mgr. Empno determines (Deptno, Job). So Empno -> (Deptno, Job) ->Mgr
EMPNO ENAME JOB MGR HIREDATE SAL COMM DEPTNO
So I would remove Mgr from this table and create a new one with Deptno, Job,mgr
November 25, 2020 - 5:40 pm UTC
That would be true if MGR was the department manager. But it's the employee's manager - this is an attribute of the person. EMPNO determines MGR. So it is in 3NF.