Must we also create separate tables?

#91

On Oct 26, 4:00 pm, Sru... (AT) gmail (DOT) com wrote:

Quote:

greetings

My book claims that for table to be in 1NF, we must:

* Eliminate remove repeating groups of data
* Create separate tables for each group of related data and identify
each row with a unique column ( the primary key )

I know that for table to be in 1NF, we must remove repeating groups
of data. But is it ( for relation to be in 1NF ) also required to
create separate tables for each group of related data or is that just
recommended and thus optional?

Say we have non-normalized table STUDENT:

STUDENT ( STUDENT#, STUDENT_NAME, SUBJECT1#, SUBJECT2#, SUBJECT1_NAME,
SUBJECT2_NAME, TEACHER1_NAME, TEACHER2_NAME )

I realize best thing to do would be to create two tables:

STUDENT-SUBJECT ( STUDENT#, SUBJECT#, SUBJECT_NAME, TEACHER_NAME )

STUDENT ( STUDENT#, STUDENT_NAME)

But would the following table also be considered in 1NF:

STUDENT ( STUDENT#, STUDENT_NAME, SUBJECT, SUBJECT_NAME, TEACHER )

I realize the first option is much better, but my book gives an
impression as if separate tables must also be created for related
repeating groups of data in order for table to be 1NF compliant. Which
doesn't make sense.

thank you

Its probably more dependent on your instructor / boss than it is being
a real technical issue. Repeating groups are starting to be
implemented by even mainstream rdbms's. Often trying to be strictly
compliant to relational theory will actually cost you a bit when
trying to actually get work done. Just an opinion tho.

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Must we also create separate tables?

comp.databases.theory comp.databases.theory

Re: Must we also create separate tables? - 10-31-2008 , 02:06 PM