Re: Database schemas
Date: Sun, 5 Sep 2004 17:07:34 -0400
Message-ID: <iMydneeGsLmgHabcRVn-qA_at_comcast.com>
"James" <nospam_at_nospam.com> wrote in message
news:znsz60b1usqr$.ymccbnqkfau8$.dlg_at_40tude.net...
> if I was creating a
> database tomorrow, would I care about the schema?
You bet!
If you "create a database" all you have is an empty shell.
If you do something like "CREATE TABLE", the DBMS does two things: it
actually creates the internal data structures necessary to store the rows,
when they come along later. And it also records the existence of the table
in the schema.
Those internal data structures are typically transparent to the programmers.
You could change things (like tablespaces) around, and their programs
would run without any changes, except maybe for performance. But if you
ALTERED the table
say so as to drop a column, now any query that uses that column is broken.
If you are studying Oracle, one of the things you need to learn is what is stored in what Oracle documentation calls the "Data Dictionary" or the "System Schema". This is a little obscure at first, until you get the idea of using metadata to describe data definitions. But it's enormously powerful. Received on Sun Sep 05 2004 - 23:07:34 CEST