Multiple table with the same primary key (design issue)

hi
i am new to database design and facing a problem.

is it better to have a table with 20 column and a primary key "USER_ID",
or have three smaller tables each with the same primary key "USER_ID"?

ie.

1st choice
table A
primary key USER_ID
column USER_ID 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20

or
2nd choice 3 tables
table B.1
primary key USER_ID
column USER_ID 1 2 3 4 5 6 7

table B.2
primary key USER_ID
column USER_ID 8 9 10 11 12 13 14

table B.3
primary key USER_ID
column USER_ID 15 16 17 18 19 20

i would like to know which choice is better for the performance?, issues with indexing?, any pros and cons?

the database i use is oracle 8i and 9i on solaris and linux

thank you very much Received on Tue Apr 02 2002 - 21:07:52 CEST