Oracle, what?

Oracle is a relational data base (DB).It is a program that use the relational model (proposed in 1969 by Edgard Codd) based on predicate logic and set theory.

Table’s data are treated as sets: so you can have the set of users, the set of employees, the set of books, the set of cars etc.

“Links” between these sets are logical “operation”, are relations between them, and define new sets: the set of books read by users, the set of cars owned by employees.

For the rest of us: Oracle is a system that can read and write data in a very efficient way. What Oracle does is to use files in a very efficient way and to hide this complexity to the final user…to you!

Each time you write a query and access a set (that is read a table’s data) you are telling Oracle to read at least a file.

Each time you write an “expression” that modify a set (that is write, change or delete table’s data) you are telling Oracle to read at least a file.

That’s more or less what Oracle do!

An Oracle blog on the basic

Yep!

Finally I found a motivation to work again on this blog.

The idea is to write on basic Oracle concept and to create a kind of “Introduction to Oracle”.

Hope that it will help.

A new Begin

After more than one year I decide to restart this blog!

Now, here I want to talk about Oracle basic concepts.

Hope to bring a bit of fun in Oracle Universe! ^_^

So this is a new Begin, with the hope that it will not be just:

Begin
Null;
End;
/

Multitable Insert

So, let’s start with two normal inserts:

insert into tab1
select 1,1,’first’ from dual

and

insert into tab2
select 1,1,’first’ from dual

this work fine, but we got Oracle 9 and 10 nowadays so we can:

Insert all
into tab1
into tab2
select 1,1,’first’ from dual

and this give us:
ORA-00918: column ambiguously defined

A bit strange.

Explain me!

This query is slow!

(copyright by my Boss)

But how can you examine what’s going on? Can you “see” what Oracle is thinking?

Yes you can!

V$iews

Oracle, as any other DBs, has got a Catalog: internal tables and views that give you information about tables, users, sessions and so on.

One subset is the v$ views (v$iews for short) subset.

Hello world!

So here we go!

First Blog! First Post! First all!

More  or less the start of an adventure!