When does one put data into a separate table?



This is a sort of vague question.


Let's say that you have a db with a "personnel" table.

Personnel_ID INTEGER PRIMARY KEY,
First_Name VARCHAR(30) NOT NULL,
Last_Name VARCHAR(50) NOT NULL,
add1..
add2..
add3...
tel..
mobile...
Language1 VARCHAR(25) NOT NULL,
Language2 VARCHAR(25),
Language3 VARCHAR(25),



Now, my question here is when does it become necessary to hive off
another table

Person_Language
ID INTEGER NOT NULL
Language VARCHAR(25) NOT NULL


The vast *_vast_* majority of people will only speak one or two, a few
3, a couple 4 and very, very few will speak 5 or more. So, let's say
we allow 5 fields in the Language part of the table, or even 6 or 7
(just to cover the Einsteins).

I'm wondering when people would both in theory and/or in practice
start to move an attribute like this off into another table? Is there
a "Golden Number" above which it automatically gets put into another
table, or how do IT professionals decide on such things?


Paul...



--

plinehan __at__ yahoo __dot__ __com__

XP Pro, SP 2,

Oracle, 9.2.0.1.0 (Enterprise Ed.)
Interbase 6.0.1.0;

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