Search

OakieTags

Who's online

There are currently 0 users and 50 guests online.

Recent comments

Affiliations

Friday Philosophy – The Answer To Everything

For those of us acquainted with the philosophical works of Douglas Adams we know that the the answer to everything is 42.

mdw1123> select all knowledge from everything
  2  /

 KNOWLEDGE
----------
        42

This above is a real SQL statement (version 11.2.0.3, just in case you wanted to know :-) ).

This was prompted by a silly discussion at lunch time about the answer to everything and databases and I wondered aloud how you could go about getting Oracle to respond with 42 when you “selected all from everything”. My colleagues looked at me like I was an idiot and said “create a table called everything with a column called all and select it”. Yeah, of course, and I laughed. So much for being an expert at Oracle huh?

Well, I tried. It did not work:

mdw1123> create table EVERYTHING (ALL number not null)
  2  /
create table EVERYTHING (ALL number not null)
                         *
ERROR at line 1:
ORA-00904: : invalid identifier

Damn. It’s a reserved word. But for what? Off the top of my head I could not remember what ALL is used for in Oracle select syntax. Never mind, I could get around the issue to some degree by the use of quotes around the column name (and just for fun, I made the column name lowercase too – this is how you can create lowercase columns but you have to be careful with this, as you will see below):

mdw1123> create table everything ("all" number not null)
  2  /
mdw1123> desc everything
 Name                                                              Null?    Type
 ----------------------------------------------------------------- -------- --------

 all                                                               NOT NULL NUMBER

mdw1123> insert into everything values (42)
  2  /
mdw1123> select "all" from everything
  2  /

       all
----------
        42

-- but be careful of case
mdw1123> select "ALL" from everything
  2  /
select "ALL" from everything
       *
ERROR at line 1:
ORA-00904: "ALL": invalid identifier

I was not happy with this though, I was having to put the quotes in my line and be careful about the syntax.

So, what is the word ALL used for? A quick check of the SQL reference manual:

It is the opposite of DISTINCT and the default, so we never have to put it in the statement.

With the above in mind I was able to quickly come up with something close, but not quite, what I originally asked for. See below for how.

mdw1123> create table everything (KNOWLEDGE NUMBER NOT NULL)
  2  /

mdw1123> insert into everything values (42)
  2  /

mdw1123> select all knowledge from everything
  2  /

 KNOWLEDGE
----------
        42
mdw1123>

Having said it was not quite what I had originally set out to do, I actually prefer this version.

Of course, I cleaned up after myself. It feels odd typing in commands that have an English meaning that would not be what you want to do – I could not get over the nagging feeling that the below was going to cause a lot of data to disappear :-) :

mdw1123> drop table everything purge;